For the possible further developed version see here.

• Official web-page: https://delta.chat/
  
• Public Support Forum: https://support.delta.chat/
• Github: https://github.com/deltachat

development repositories and also Delta.chat discussions in general

A topic on the origin of this manual can be found at Delta Chat's support forum: “Comprehensive Manual for DC” and at sangham's forum. One should feel always welcome to expand the manual and/or contribute corrections if feeling inspired.

One can download the Delta-Chat software for serial platforms.

If up to install a new version it's recommended to first make a backup of your existing data and settings.

Once you have installed Delta-Chat the welcome page appears.

Use “Log in to your server” to setup your account by using your own email. (This option is also used for additional accounts later, under switch account in the main menu available) There is no use of any third-part server, registration, and no connection to resources other then your own email-account.

The setup for additional accounts, found in the main-menu works similar and you can setup multiple accounts as you wish by later add account use, under switch account.

If not having an email account, Delta-Chat has an informative list of email-provider.¹⁾

Usually simply enter your email address and your server-password (it will not be shared and stays at your device only) is enough for the setup. The auto-progress might require some time.

Certain provider require to get into the advanced settings

This is used to join a certain chat via previous shared OR. The will be upcoming additional different use as well.

After having chosen this action hold the device camera above the image. It will recognize it by itself.

In addition the scan possibility can be found as icon in next the main menu on the chat-list page in the main-header.

For share and inviting via OR code see chat-menu.

When one sets up an additional device to use Delta-Chat in synchronized way, or if a new Installation is undertaken, or if installing other versions, like Delta-Chat Dev, this way will import you previous Backup. Be sure, if it is not found automatically, that the backup is found in the device's download-folder.

If there are more backups, the software will select the latest. If you import backups for more the one account (each account currently requires separate backup) it's required to delete the already installed. Otherwise it would always the last. Details on it see backup, available in the main menu under settings » chats and media to be executed.

Most settings and options are found in the two menus:

• Main Menu
• Chat-menu

Additional menus are:

• Action-menu
• Profil-menu

On the top right corner one finds the main menu, below the chat-list, giving following chapters:

• New Chat
• Contact requests
• Settings
• Help
• Switch account

Following the single functions in detail:

This option can be either addressed via the main menu or (only for mobil apps, not on desktop) via the (+)-button in the right lower corner of the chat-list.

By choosing this option a list, containing all (detail?) contacts appear. By clicking a certain contact wished messaging can be started.

Additional one can also create a new group or verified group to lead a conversation.

In cases where a contact does not exist now, best to use the upper line for search to write a new email inside and then push the + next “New contact”.

More in regard of storage and origin of addresses see address-list

Clicking “contact requests” in the main menu, messages which are related to a certain chat, single or group, would be displayed on a new page opened. Whether new contact request would be displayed or not depend also on the settings in chats and media, whether “all” is set in Show classic email or not.

Clicking on a message there one is asked whether to accept by “ok” an, or “block” a maillist (Newsletter) or a contact.

Accepting to “chat” with a new contact opens an new chat and it's not necessary to response in this chat to have it then listen in your chat-list. For Maillist no replay to the sender is possible but most other actions with messages found in the action-menu once accepted.

Once blocked this contact can be found then in Blocked contacts and it's possible to unblock it there.

Contact requests are usually also shown at the beginning of your chat-list and can be accessed there as well, yet one by one directly.

The settings are found in the main menu, displayed below the chat-list.

Following main chapters are found here:

• Your Profil Info
• Chats and media
• Notification
• Appearance
• App access
• Advanced
• Help

Here you can edit you display name, signature attached on each email (not displayed in chat messages via the app) and avatar.

Also Password and Account can be edited here, aside of the access via switch account.

Once you have finished to edit your profil setting, click the ✅ in the right upper corner to return done with your action.

Dev: (?)

Chosen name will be displayed on receiver side in addition to ones email address and possible saved in others address-lists.

By default “Sent with my Delta Chat Messenger: https://delta.chat” will be attached after the text in one's send email. One is given to edit it as wished.

By touching the default auto-avatar (colored circle with initial character) one can chose another by serial (and variable) devices possibilities, using one of the suggested. The avatar will be send as attachment with every email and possible get stored on receiver side. Naturally such can not be made undone for already send messages.

Allowed file-formats: jpg, png,…(?)

Settings under “Chats and Media” allows one serial setting in regard of general behaviour of use and save-opinions for messages generally:

• Show classic email
• Blocked contacts
• Read receipts
• Enter key sends
• Outgoing media quality
• Delete old messages
  • Delete old messages from device
  • Delete old messages from server
• Backup

Following options are available:

• No, chats only

only email in the delta-chat folder on your server will be displayed in your chat-list. No contact requests (?).

• Only accepted contacts

others emails would not appear on the app.

• All

Emails of other then existing chats would appear as contact request or found under this main menu option.

Tips & Tricks:

• How to get all, also older, messages into ones app's chats?

Here one can find previous blocked contacts set via the action block contact in the contact menu, and also make the unblocked.

Enabled one allows to give info-email back on request whether others incoming messages had been received or not. This email reports status to be seen under info-action used for a message. By default this option is enabled.

Note: If this is disable one wouldn't receive an info about other, and not only not giving info on request.

By default this option is disabled to allow usual line break by the use of enter key. Some may like to use the enter key for the action “send” instead of clicking it's icon. In this case it needs to be enabled.

(Alternative key-combination for line break when enabled?)

To save traffic and server space, maybe not only to save money but remembering the heat it causes globally, one can select different kinds of media quality for the attachments.

You can chose between:

• balanced (size?)
• worse quality, small size (size? if fine with modest)

Here one can set time periods after which ones send and received messages would be deleted from ones own store. If searching for ways to common agree of deleting messages (means also on others devices and/or server, try out the “disappearing messages-option” in the particular chat-menu

Deletes all messages on ones device after the chosen time period. Separately saved messages elsewhere can be not effected by this.

Likewise the option “Delete old messages from device” does this to execute such for messages on the server found in the Delta-Chat folder.

To create a backup for possible import of backup-action, one can use this option found in the settings under “Chats and media”. It will save all messages, contacts, important setting and you end-to-end Autocrypt setup in a zip-file on you device in the download folder like “”delta-chat-backup-2021-02-20-00.tar“”. The last two numbers may go up to 01, 02… if there are more then one backup made. Important! Delta-chat does not make only one backup for all your accounts but it's required to make a backup on each account separately. Good to remember which account's backup was made first to know which is for which account.

One may use a backup for:

• Safty-backup
• When on installation of a new version or anew.
• To synchronize between different devices
• Serial Autocrypt setup undertakings

See also import backup under setup.

Under this category in the settings one is able to customize one's preferred way becoming notified.
Following options are found here:

• Notifications
• Reliable background connection
• Sound
• Vibrate
• LED color
• Show
• Priority
• In-chat sound

Be sure that notifications are enabled in general advice settings if wishing to use them.

Here one can turn notifications generally on and off. By default “on” is set.

This requires to turn on notifications and ensures connection best as possible. See also: killing apps and battery use. Once enabled the Delta Chat logo in the notification area is shown gray permanently.

Here one can chose an available notification sound from one's device. Chose equal named actions also for particular sound for a chat or contact in the profil-menu.

Activates vibration (in addition) if the device allows such. Settings can be made also to activate vibrate for single chats or contacts via the profil-menu.

Activates the LED notification (in addition) if the device allows such. From various colors can be selected ones preferred.

An option to chose which information will be displayed when notified.

• Name and message (title), or
• Name only, or
• No name or message.

…can be activated

Here you can order different effort to win over other processes in regard of your Delta-Chat notifications on your device.

Select sound to be heard for incoming messages when particular chat is opened or app else active used.

By default one can use delta-chat's set of emojis, available left of the Message-editor.

In this setting one can disable it's use.

Some accesses in regard of wished security can be set here:

• Screen security
• Incognito keyboard

Enable this option to avoid best that screenshots of messages and lists are made.(?)

This option enabled hinders possible set auto-learning of keyboard while typing be disabled to avoid cache of text passages or words elsewhere on you device.(?)

A large set of advanced settings is also available, dealing from autocrypt setup till access to a log-file.

• Prefer end-to-end encryption
• Send Autocrypt setup message
• Manage Keys
  • IMAP folder handling
  • Watch inbox folder
  • Watch sent folder
  • Watch Delta Chat folder
  • Send copy to self
  • Automatic moves to Delta Chat folder
• On demand location streaming
• Video chat instance
• View Log

End-to-end encryption allows “secret” communication between two devices directly. This means encoding/decryption happens only on ones and the other device and nowhere else. This requires the sending and receiving of a key which is usually made automatical with the fist email contact but can also made in manual ways of exchange with the import backup and backup tasks…(?)

(?)

Using this option one can export keys and import keys for the serial activities possible required for end-to-end encryption.

Those options allow you to chose which kind of email will appear as messages within your Delta Chat app. Those settings are related with the settings under Show classic email. (?)

To get informed when email arrive in your email server inbox which are not from recognized contacts or chats yet (would possible not automatical moved in Delta Chat folder). Emails may then appear in contact requests) (?)

Likewise above for sent folder server-side. (?)

Likewise above for Delta Chat folder server-side. (?)

Enable to save a copy of outgoing messages as email on your server. Useful if wishing to access them also when using multiple devices.

Enabled moves all emails, as soon as recognized contacts (?), into the delta chat folder on your email-server.

Using together with the options given under map one may allow to access to one's location.

Here one can set an instance (web address) of a video chat server. Details see video chat server.

If required to know what has been going on behind the screen: Here a log where infos are stored.

In advanced settings menu the same target is reached by clicking it. Under it, in the setting menu, one finds the version of ones app. Useful to share when asking for help in the Support forum (https://support.delta.chat).

How ever… it directs one to the offline FAQ-list and maybe something like this here in times to come.

One is able to set up multiple accounts using separate email. Here, in the main menu one can switch between accounts.

Important! Currently all actions and settings have to be made for each account, as well as backup and import backup.

If wishing to add new account, working similar like described in setup, select this option.

This action can be reached via the main menu's switch account option. Be careful in using it. (? Impact)

On each chat or conversation page a menu is found at the right uper corner containing following options:

• Search
• Disappearing messages
• Mute Notifications
• View profil
• Add Attachment
• Leave Group
• Archiv Chat / Unarchive Chat
• Delete Chat

…and are discussed in detail below.

This function, found in the chat-menu, allows one to search text-strings within a chat and highlights messages containing the string for a short while. In cases where the string is found in a quoted part of a message colored highlighting wouldn't appear (a bug?).

Another feature in all recent Delta Chat versions on all platforms are the so called Disappearing messages, similar to the Signal-messenger offering. This function, a group- or chat-setting, change-able by all group-members, can be selected in the particular chat's menu, can be set separately for each chat.

Once the feature is enabled in the settings, any user can decide to see all subsequent messages disappearing.

After a chosen timeout, the later send messages of this chat will disappear on all the users devices, on the users server - and moreover, also on devices and servers of the other group members, if they are using Delta Chat. So when nobody made any copy, backup, screenshot or forwarded such kind of messages elsewhere, they disappeared.

Note: The Delta-Chat app must be active and connected with the Internet to execute the deletion timely. If this isn't the case, deletion on each user's side of the group, would be done only as soon the app would be active and connected again.

• The settings effect all of the group's messages in the particular Chat or conversation.
• Messages within the are deleted after set period on all devices and email-server of the group members using Delta-Chat software.
• Old messages, previous the setting, are not effected. Change of setting effects also just new messages till possible changes again.
• All members of a Chat or conversation are informed by an info about one's new settings set in the chat and can change this setting like-a-like every time.
• Group members, not using Delta-Chat wouldn't have ones messages deleted after the set period, as it requires the delta-app for execution.
• As personal info and reminder a small clock-image appears in the Chat-header.

• A handy way to avoid not necessary usage and messy of storage resources on many places effected by ones shares.
• To delete ones messages after having done it's use, out of what ever reason.
• In cases where discretion might be required, or appearing of told would harm oneself and/or others afterward.

Note: Like all ways of outwardly protections are fragile, this option is no guarantee that no copies, forward, screenshots… had been made of thought being disappearing messages. So good to stay secure by ones conducts in not harming anyway. Done can never be made undone.

Discussions:

• Function of “disappearing messages” from a data-impact consideration mainly
• …

Dev: This action sets Ephemeral-Timer: *time in seconds* in the header of messages.

Corresponding codes: link?

See Mute Notifications in the profil-menu.

The action “view profil”, found in the chat-menu leads one to the chat-options and can be reached also by clicking the group-image in the chart-header.

It's possible to add attachments, files, to ones message. One can either chose this possibility available next to the message-editor - writing afterwards a message optional to it - or, if one has started to write, select the option in the chat-menu. The attachments previously shared in a chart can be viewed and/or searched in a list in on the chat-options page. There are many ways to select a source, also depending on ones device and settings.

On clicking this option in the chat-menu, an info whether sure about it will be appear, since you can not join again easy by your self unless another would invite you, or you still have the invitation OR code:

Once pressed “yes” a message about the leave would be send to all and also appear on you chats-display:

Although you still can open the chat, you would no more receive new messages from it as well not able to write in this group. So maybe you like to consider to simply mute notifications from it, if currently stressed by messages from it.

One has the possibility to select “Archive Chat” in the Chat-menu. This action would put this chat in the background of the chat-list and no more appear on it, only found at the end of it in the archiv folder.

If clicking there, the “archived chats”-folder would open and by clicking the “archived”-info of a particular chat, that chat could be opened, possible to unarchive.

By the action “archiv” nothing is removed from your email-server nor from your device but simply brought out of direct view at you chat-list.

Here you find all previous archived chats.

One can “unarchive” a chat via the “archived chats”-folder, getting an alternative option to “archive in it's chat-menu.
Once done the chat will again appear in your chat-list

Once chosen this opinion the delete a chat, since it could not be made undone easily, one would get an information that this action causes the messages and chat-infos to be deleted on ones device (not on the server), and asked whether progress or not:

If maybe being out of signs of a particular chat would be enough, consider using to archiv chat or just mute notifications from it.

The profil menu on the profil page is found via view profil in the chat-menu. In the header of the main profil page, clicking the three dots icon, one finds following options to chose:

• Group image and name
• Mute notifications
• Sound
• Vibrate
• Encryption

Similar menu is also found under each contact. See contact-profil.

The page for profil-settings is found in the profile-menu and allows to set the group's image, group-image and group-name by every group-member every time, also anew.

Here one can add or edit the group's name and by clicking on the Avatar select a picture found on the device. After selecting the file one is leaded to a simple avatar-editor. Here one can size and crop the image and accept it by clicking “Done” in the right upper corner.

Once fine with the settings, click on ”create group“ to save the setting. An info-message would be send to each member and displayed in the chat including who performed the action.

The profil page can be also reached by clicking the avatar in the chat-header instead.

That option can be also reached via the chat-menu. If you feel to much disturbed by a chat's messages, instead of thinking to leave a group (since not easy to join again without a member adding you), one has the possibility to mute chats. No notifications would be arising for chosen time.

• Mote for 1h 🔀
• Mute for 2h 🔀
• Mute for 1 day 🔀
• Mute for 7 days 🔀
• Mute forever 🔀

An icon would appear in the profil-header and in the chat-list as well. This settings can be changed and unmute made in the chat-menu as well. Nobody would be informed and possible stressed about this “leave” for a while.

… or unmute

Is avaliable if a certain chat has been set to ”mute notifications“ before, makes notifications as set in the settings avaliable again, and can be reached in the chart-menu.

One can select a custom sound for each contact-profil- or chat-profil. This option will open to your possibilities to reach storages on your device for selecting a wished file. Supported audio-files are mp3,…(?). See also sound in the general settings.

It's possible to select notifications by way of vibrate for each chat or contact in the profil-menu. One can chose between:

• Default

Option to vibrate turned on or off like set in the general settings.

• On
• Off

See also vibrate in the general settings.

Clicking this option one gets and information how end-to-end encryption has been set for each group member or how it is set when current viewing the profil of a single contact.

A participate contact might currently run:

• “end-to-end encryption preferred”
• “end-to-end encryption available”
• or “no encryption” (standard, if another doesn't use Delta Chat)

To see the fingerprints, keys, you exchanged with a particular member, chose encryption in the single contact profil.

The profil of the single contacts contains similar menu as View profil for chats, except the options for setting notifications, as sound and vibrate settings if this contact does not use Delta Chat, but can be set within single chats. See for more: View profile.

• Edit name (see your profil info)
• Mute notifications (see view profil for chats)
• Sound (…)
• Vibrate (…)
• Encryption (…)

In addition it maintains the action

• Block contact

It's currently not possible to set a contact-avatar manual, and depends on whether the contact has added a picture by himself or not. By default colored circles with initial character of the contact name are displayed if sender hasn't set a personal avatar.

Allows to change the displayed Name (usually email address if non is set) of certain contact in the contact profil but also in the chat-profil in combination with setting an avatar, and called ”Group image and name“

One can block single contacts within the contact profil. The collection of blocked contacts, also to unblock them, is found in the main-menu under Chats and media in the general settings.

Aside of certain actions for particular displayed messages in the chat-menu, some other actions can be performed after marking one or more messages within a chat.

To mark a message, for certain action, as selected, touch the area of it's row a little longer till marked blue (best outside the message's frame). Then icons for action appear instead of the chat-header.

Once one message is marked this menu for message actions will be displayed (incl attachment is selected:

Once more then one message is marked this menu for message actions will be displayed:

The number informs about the amount of selected messages. Clicking the arrow the selection is undone.

If wishing to replay to the selected message, use this action. The message will be quoted in your message.

Note: Quoting can also be made by wiping a message to the right.

Pushing the info sign one gets detail infos on selected message. More on it see message info.

Use this to delete selected messages from you device and server. One would be asked another time before performing the action.

Note:_ Delete can not made undone.

Use this action to save a picture, voice-message or document/file attached to a selected message.

This copies the message text (without quotes) to the clipboard for further use.

A message can be forwarded to another chat. Once clicked you can chose in which chat or chats to share it, back in the chat-list, by select the wished. It's also a way to save messages in the folder ”saved messages“

This is found as selection under the three dots and used to answer direct to the message sender in a new chat

Main collection of Download and info on public download: https://delta.chat/de/download

Source Code can be found here.

Minimal requirements: Android 4.1
Changelog

A given Android version, dedicated toward the Sangha and it's follower, can be downloaded here: https://forum.sangham.net/index.php?action=tpmod;dl=item757

Source Code can be found here.

Minimal requirements: iOS 11, iPhone 5s or iPad 5/Air/Mini
Changelog

Source Code can be found here.
Homebrew manual install: brew install –cask deltachat

Minimal requirements: macOS 10.10 Yosemite
Changelog

Source Code can be found here and there is also a experimental portable version.

Minimal requirements: Windows 7
Changelog

Known issues: Windows Defender reports malware²⁾

Flatpak manual install: flatpak install flathub chat.delta.desktop
Arch manual install: yay -S deltachat-desktop-git

Source Code can be found here.

Minimal requirements: Ubuntu 12.04, Fedora 21 or Debian 8 or compatible systems
Changelog

Here one can find the last version from the eager working Developers: https://download.delta.chat/android/nightly/

Discussion and info on Use of nightly-versions android

For Android, you can verify the signing certificate on the APK matches one of the following SHA256 fingerprints:

For F-Droid downloads: 9D:B6:67:8E:D7:4C:88:12:4B:82:5E:8F:90:50:2B:76
CD:97:C5:EC:CC:9A:A9:2F:40:33:02:71:02:D9:AA:9D

Other APK downloads: D6:41:54:2B:F7:E7:73:F5:BA:7B:97:79:4D:E0:14:21
2F:49:91:AE:97:15:EE:42:0B:16:F3:04:35:84:17:35
or 35:5B:E2:C3:8E:C6:73:83:C1:02:FB:E0:3E:84:C4:BC
3E:6F:89:06:F8:D3:66:91:4F:84:52:82:08:13:2A:EE

To print the SHA256 fingerprints of the APK signing certificate you can use eg. keytool -list -printcert -jarfile <APK-file>

This section contains defined expressions not found under certain menu option and explains them.

An account for the use of Delta Chat requires an own email account which is used for store your messages as usual email. No register on any third part server required.

One can uses multiple accounts (email accounts), each separate, to easy communicate.

For how to set up an account or add additional see setup, backup and import.

If you delete one or more accounts on the Delta-chat app wouldn't effect your data on your email-server.

For help or advice to gain an email-account good useable with the app see email.

DeltaChat (android and iOS) reads contacts from the system address-book (Q: of the device?) when the user allowed (Q: where? app-access?) it to access that list.

In the newer versions it also loads contacts of previous emails that were sent from that email account (Q: server-side).³⁾.

Info: Currently there is no option to import into, or export from the app's address-list.⁴⁾

Messages allow also to add attachment(s). The maximum size for such files to be send is 49.1 Mb (?). Received attachments can be saved separately (by downloading them to ones device) and collected viewed in either the chat-gallery or the list of chat-docs of a particular chat.

Related action: add attachment in the chat-menu

Related setting: Main menu » settings » Chats and media » Outgoing media quality

See voice-message.

…or Contacts:

“Contact” denotes a conversation partner via a certain email stored in the app's address book. A list of available contacts as well as the possibility to add a new contact is given within the option new chat. See also address-list for further infos.

Denotes either a group conversation or a conversation between two people. A chat is technically a selection of emails under one certain topic. See also details under menu option New Chat.

See: chat

The colored block on the top of the screen is here denoted as “Chat-header” and displays the chat-name, possible a clock-image showing that the option disappearing messages for this chat is activated, as well the number of the current group-members and the group-image.

By clicking the group-image, the chat-options and list of group-members become available. The three-dot chat-menu can be accessed as well here.

For each group an own avatar can the selected. By selecting group image and name in the profil-menu upload and edits can be made.

Those can be accessed by clicking the group-image in the chat-header of the chat-profil page. Next to the list of members one finds here also the lists chat-doc and chat-gallery.

Under the options the group member list is found.

The list of a chat's file-documents, previously shared by it's group-members, can be accessed via the page for chat-options. It contains all (?) files shared as attachment excluding shared pictures, which are found in the chat-gallery.

The list of a chat's images, previously shared by it's group-members, can be accessed via the page for chat-options. It contains all (?) images shared as attachment. Other shared attachments are found in chat-doc.

Denotes the equipment one uses to run the application or one “end” of an ”end-to-end encryption talk.. Serial environments are supported and an overview of device-systems can be seen under download.

Is a folder found in the chat-list and contains default by installation or update of the version an info-“message” about new features.

As the folder actually just reports device-side infos, they aren't send by anybody else then the app-software on your device. Notifications about problems with login to your email-account, for example, may be stressed out here. One can of course not replay to those infos-messages as it is actually not a normal chat.

… or email-account:

The apps use is based on using your own available server, your email-server(s). Register an account does not require a new but using what one might already have or gain newly where ever wishing to store ones communication Data.

For which providers work well with Delta Chat an informative list of email providers is available.

When register an account for using the app on certain email address one gives the app the possibility to connect one to own email server but wouldn't share all with anybody or elsewhere at all. All stays either on your device or on your server.

Denotes the email address of a certain contact, or one of your used email addresses for each of your account. An/your email address as well as the password to your email-server is required to setup a new account. Contacts, if no custom name has been set in “edit name, are displayed by their email address in the chat-list as well as in the contact-list.

If one does not have an email account or likes to know which provider serves good conditions for Delta Chat's use, here an informative list by the App-developers: Provider Overview. The list contains also hints and tips for supportive settings.

The Venerable members of the Sangha and it's faithful followers are given to request a donated email account and are given to do so via the online monastery sangham.net or via SMS, sending “need email account for *your Name*” to +855 12345025. Access-dates would be likewise send.

Delta-Chat comes with a set on emojis, set as ”use system emoji“ by default. If disabled in the appearance-settings standard emojis according to ones device setting would appear.

Groups define the participator of a particular chat, the group-members, the list of email-addresses receiving the mails. In addition to create a name one can define also a group-image.

Select New chat and then (+) New group from the menu in the upper right corner or hit the corresponding button on Android/iOS.

On the following screen, select the group members and define a group name. You can also select a group avatar. As soon as you write the first message in the group, all members are informed about the new group and can answer in the group (Note! As long as you do not write a message in the group the group is invisible to the members).

Every group member has the same rights as any other. For this reason every one can delete every member or add new ones.

To add or delete members, click on the group name in the chat.

…or Group member/Group-members:

Are selected members of a group or chat. They can be added or removed by any member of the group. Messages shared within a chat are delivered to all members of it. Thought it's always possible to answer on a message privately. There is no such as an admin within every chat and all share the same possibilities. Group members need to be always invited, added by someone within particular Chat. See ”Add members to a group“ and ”view profil“ in the Chat-menu.

It denotes the name of a group, e.g. the name of a chat. It can be edited in the chat-header and is initially set when creating a new chat in the chat-list.

The main-header shows the app-name on the left and gives way to search, to OR-code, and the main menu.

The inbuilt text-editor allows one to direct contribute to a chat.

On the left, next to the text-field, one finds the option to select emoji, if use is enabled in advanced-setting. One can also add attachment of files, clicking the green icon, record a voice-message by pushing the microphone-image, or take direct a picture to be attached, using the camera-sign.

Detail informations about the status of a message can be gained via the action-menu by clicking the info icon. How ever:

…in the right lower corner of each of ones send messages in a chat certain Info's on status of delivery would be shown, next the time it was send:

A single tick tells one that the message was successful send.

A double tick tells one that the message was successful send and at least 50% of the group-members have opened the email containing the message (see also ”read receipts“ in the settings).

A small circle tells one that the message is still pending and didn't leave the outbox, or not to all all recipients could be reached proper. Clicking ”info“ in the action-menu may lead to more details or look into error mail delivered in your email inbox on it.

The red Info-sign tells one that not all went well with one's message sending. More about it can be view by marking the message and select ”info in the action-menu.

If a small lock appears next the sending date in a message means that you transfered it with end-to-end encryption with (all of) your conversation partner(s). For more on it see: Encryption.

Delta Chat allows to run it good synchronized on more then one device parallel. See Multi-client in the FAQ for more about multiple devices use.

Recommended to activate the setting “send copy to self” to have outgoing messages available on all devices used.

There are three kinds of profil-pages, yet the general function and layout is similar:

• Own Profil
• Chat-profil
• Contact-profil

See “Your Profil Info”. It can be reached via settings.

This profil can be reached by clicking the related avatar. Then chose “view-profil” in the chat-menu.

Similar the chat-profil and can also be reached by clicking the related avatar. See Contact profil.

Used for:

• Inviting via OR

One can scan OR code to access a particular chat via a given OR image. Within the chat-profile, reachable via “view-profil” in the chat-menu the corresponding OR for a chat can be found and shared letting others join the group.

One can use the OR here to join the chat “Comprehensive Manual Delta Chat” - if still existing - by pressing the image and chose “share”, whereas Delta Chat should open. (?)

Topic in the support forum: [Manual] OR code (tips and tricks), and bugs?

This folder, visible in the chat-list contains separate saved messages. With the option forward in the action-menu messages can be brought here by selecting this folder. This possibility gives ways to:

• Forward messages here for easy access
• Take notes or voice memos
• Attach medias to save them

Although the text-editor is available, the send-button here serves just to save a massage with this “chat”-like folder. Of course one can send by forward out of this box, or use the “chat” for talks with oneself herein.

When spoken about “server” here no central or any large companies server is meant but your own email-server. There is not server storing anything maintained by the app developers and one stays free to chose where one's communications are stored beside of one's device. Access to your server is needed for setup an account to make use of the email-messenger. See some detail under email provider in cases not having an email account yet.

It's more then comfortable to record voice as a alternative contribution to a chat, using the camera-sign next the message-editor. As long the sign stays touched on, recording endures. Once released the record would be saved and also send right after. Voice messages can be shared and stored like other attachments easily.

Files are produced and saved in aac-file format and those voice-messages can be separately saved by marking in in the chat and select the save-option appearing in the chat-header. Listen: 2021-02-21-08-11.aac

Frequently Asked Questions

• What is Delta Chat?
  • How can I find people to chat with?
  • What are the advantages of Delta Chat compared to other messengers?
  • Which messages do appear in Delta Chat?
  • What about spam?
  • Does Delta Chat support images, videos and other attachments?
  • Who sees my profile picture?
  • Does Delta Chat support HTML e-mails?
  • Why do I have to enter my E-Mail password into Delta Chat? Is this secure?
  • Which permissions does Delta Chat need?
• Groups-Questions
  • Creation of a group
  • Add members to a group
  • What is a verified group? Why is it experimental?
  • I have deleted myself by accident.
  • I do not want to receive the messages of a group any longer.
  • What do double ticks mean in group messages? Has everyone read my message now?
• Encryption
  • Does Delta Chat support end-to-end-encryption?
  • What do I have to do to activate the end-to-end-encryption?
  • If end-to-end-encryption is not available, is the connection not encrypted at all?
  • How can I verify cryptographic status with a sender?
  • How can I check the encryption of messages?
  • Which standards are used for end-to-end-encryption?
  • What is the difference between verified groups and 1:1 chats with verified contacts?
  • Does Delta Chat support Perfect Forward Secrecy?
  • How does Delta Chat protect my Metadata?
  • Can I reuse my existing private key?
  • I can’t import my existing PGP key into Delta Chat. Why don’t you use pEp (pretty easy privacy)?
• Multi-client
  • Can I use Delta Chat on multiple devices at the same time?
  • Are there any plans for introducing a Delta Chat Web Client?
  • Why can I choose not to watch the Inbox?
  • What is the “Send Copy to Self” setting good for?
  • Why can I choose to watch the “Sent” folder?
  • Why can I choose not to watch the DeltaChat folder?
• Miscellaneous
  • Does Delta Chat work with my e-mail-provider?
  • If Delta Chat uses E-Mail, is it really an Instant Messenger?
  • Is Delta Chat compatible with Protonmail / Tutanota / Criptext?
  • I’m interested in the technical details. Can you tell me more?
  • How are Delta Chat developments funded?

… or Delta Chat

Delta Chat is a new chat app that sends messages via e-mails, encrypted if possible, with Autocrypt. You do not have to sign up anywhere, just use your existing e-mail account with Delta Chat.

With Delta Chat, you can write to every existing e-mail address - even if the recipient is not using the Delta Chat app. No need for the recipient to install the same app as yours, as with other messengers.

• Independent of any company or services. You own your data.

Your data is not saved on a central server unless all users are using the same e-mail servers.

• You do not distribute your address book to anyone.

• Fast by the use of Push-IMAP.

Largest userbase - recipients not using Delta Chat can be reached as well.

• Compatible - not only to itself.

Elegant and simple user interface. Distributed system.

No Spam - only messages of known users are shown by default.

• Reliable - safe for professional use.
• Trustworthy - can even be used for business messages.
• Copyleft and Standards based libre software.

Delta Chat automatically shows:

• Messages from contacts in your address book
• Messages from contacts contacted by you

Replies to messages sent by you Other messages do not appear automatically, and are to be found in Contact requests. If desired a chat can be started from there.

Messages in common spam folders are ignored and contained addresses are not considered as known contacts. As messages from unknown contacts do not pop up automatically, normally, there is no spam.

However, if needed, you can block any contact.

Yes. Beside the plain text, all e-mail attachments are displayed as separate messages. Outgoing messages get attachments as needed automatically.

You can add a profile picture in your settings. If you write to your contacts or add them via QR code, they automatically see it as your profile picture.

Contacts who don’t use Delta Chat see it as an E-Mail attachment.

For privacy reasons, no one sees your profile picture until you write a message to them.

Your profile picture isn't sent with every message, but regularly enough that your contacts will re-receive your profile picture, even if they add a new device.

Yes. If an incoming e-mail lacks a plain text part, HTML-emails are converted to plain text in the app. Outgoing e-mails always use plain text.

As with other E-Mail programs like Thunderbird, K9-Mail, or Outlook, the program needs the password so you can use it to send mails (see setup). Of course, the password is stored only on your device. The password is only transmitted to your E-Mail provider (when you login), which has access to your mails anyway.

If you use an E-Mail provider with OAuth2 support like gmail.com or yandex.ru, there is no need to store your password on the device. In this case, only an access token is used.

As Delta Chat is Open Source, you can check the Source Code if you want to verify that your credentials are handled securely. We are happy about feedback which makes the app more secure for all of our users.

Depending on the operating system in use, you may be asked to grant permissions to the app. This is what Delta Chat does with these permissions:

• Camera (can be disallowed)

take pictures and videos: for sending

Photos

• Contacts (can be disallowed)

read your contacts: to discover

contacts to chat with

• Location (can be disallowed)

access approximate location (network location sources): for the location streaming feature

access precise location (GPS and network location sources): for the location streaming feature

• Microphone (can be disallowed)

record audio: for audio messages

• Storage (can be disallowed)

modify or delete the contents of your SD card: to download message

attachments

read the contents of your SD card: to share files with your contacts

• Other app capabilities

change your audio settings: so you can choose ring tones and volume for notifications and audio messages

run at startup: so you don’t have to start Delta Chat manually

control vibration: for notifications

view network connections: to connect to your E-Mail provider

prevent phone from sleeping: so you can easier copy the security code during the Autocrypt Setup Message

have full network access: to connect to your E-Mail provider

view Wi-Fi connections: to connect to your E-Mail provider

ask to ignore battery optimizations: for users who want to receive messages all the time

Select New chat and then New group from the menu in the upper right corner or hit the corresponding button on Android/iOS.

On the following screen, select the group members and define a group name. You can also select a group avatar.

As soon as you write the first message in the group, all members are informed about the new group and can answer in the group (as long as you do not write a message in the group the group is invisible to the members).

Every group member has the same rights as any other. For this reason every one can delete every member or add new ones.

To add or delete members, click on the group name in the chat.

A verified group is a chat that guarantees safety against an active attacker. All Messages in a verified chat view are e2e-encrypted, and members can join by scanning a “QR invite code”. All members are thus connected with each other through a chain of invites, which guarantee cryptographic consistency against active network or provider attacks. See countermitm.readthedocs.io for the R&D behind this feature.

As of Dec 2019, a “verified group” remains an experimental feature. It is continuously improved and many bugs have been fixed since the original introduction in 2018. However, there remain cases, especially with large groups where inconsistencies can occur, or messages become unreadable. Early 2020 a security review is upcoming, and several new developments around qr-join protocols are taking place so chances are we remove the “experimental” label not too far in the future.

As you’re no longer a group member, you cannot add yourself again. However, no problem, just ask any other group member in a normal chat to re-add you.

Either delete yourself from the member list or delete the whole group member to add you again.

As an alternative, you can also “Mute]d” a group - doing so means you get all messages and can still write, but are no longer notified of any [[#new messages.

A message shows double ticks after more than half of the recipients have seen the message on their display. Note that some recipients might have disabled read-receipts for privacy-reasons.

If more than 50% in a group disabled read receipts, the double ticks will never show up. For more detailed information, see this blogpost.

Yes. Delta Chat implements the Autocrypt Level 1 standard and can thus E2E-encrypt messages with other Autocrypt-capable apps.

Delta Chat also supports a strong form of end-to-end encryption that is even safe against active attacks, see “verified groups” further below.

Nothing.

Delta Chat apps (and other Autocrypt-compatible e-mail apps) share the keys required for end-to-end-encryption automatically as the first messages are sent. After this, all subsequent messages are encrypted end-to-end automatically. If one of the chat partners uses a non-Autocrypt e-mail app, subsequent messages are not encrypted until an Autocrypt-compliant app is available again.

If you want to rather avoid end-to-end-encrypted e-mails by default, use the corresponding Autocrypt setting in “Settings” or “Advanced settings”.

With most mail servers, Delta Chat establishes transport encryption (TLS). This only secures the connection between your device and your e-mail server. Whereas e2e-encryption provides safety between your device and a friend’s device.

If you are within immediate distance of the chat partner:

Select QR Invite code on one device and then Scan QR code on the other one and scan the code. If both devices are online, they will introduce a chat channel with each-other (if it doesn't exist already) and the encryption keys will also be verified. Both will see a “sender verified” system message in their 1:1 chat.

If you are not near the chat partner, you can check the status manually in the “Encryption” dialog (user profile on Android/iOS or right-click a user’s chat-list item on desktop):

For end-to-end-encryption, Delta Chat shows two fingerprints there. If the same fingerprints appear on your chat partner’s device, the connection is safe.

For transport encryption, this state is just shown there

A little padlock shown beside a message denotes whether the message is end-to-end-encrypted from from the given sender.

If there is no padlock, the message is usually transported unencrypted e.g. because you or the sender have turned off end-to-end encryption, or the sender uses an app without support for end-to-end-encryption.

Autocrypt is used for establishing e2e-encryption with other Delta Chat and other Autocrypt-capable mail apps. Autocrypt uses a limited subset of OpenPGP functionality.

Delta Chat implements countermitm setup-contact and verified-group protocols to achieve protection against active network attacks. This goes beyond the opportunistic base protection of Autocrypt Level 1, while maintaining its ease of use.

1:1 chats with a verified contact and verified groups are not the same, even if there are only 2 people in the verified group. One difference is that you could easily add more people to the group, but there are other implications as well.

Verified groups are invariably secured. Any breakage (cleartext or wrongly signed messages etc.) will be flagged and such messages will not be shown in this chat. You can trust all messages in this verified-checkmark chat to have not been read/altered by middle parties.

1:1 chats are opportunistic, it is meant to allow people to communicate no matter if they change e-mail clients, devices, setups etc. That’s why there is no verification checkmark, even if you have verified the contact.

No, OpenPGP doesn’t support Perfect Forward Secrecy. Perfect Forward Secrecy works session-oriented, but E-Mail is asynchronous by nature and often used from multiple devices independently. This means that if your Delta Chat private key is leaked, and someone has a record of all your in-transit messages, they will be able to read them.

Note that if anyone has seized or hacked your running phone, they will typically be able to read all messages, no matter if Perfect Forward Secrecy is in place or not. Having access to a single device from a member of a group, will typically expose a lot of the social graph. Using e-mail addresses that are not easily tracked back to persons helps group members to stay safer from the effects of device seizure.

We are sketching ways to protect communications better against the event of device seizure.

As Delta Chat is a decentralized messenger, the metadata of Delta Chat users are not stored on a single central server. However, they are stored on the mail servers of the sender and the recipient of a message.

Each mail server currently knows about who sent and who received a message by inspecting the unencrypted To/Cc headers and thus determine which e-mail addresses are part of a group. Delta Chat itself could avoid unencrypted To/Cc headers quite and always put them only into the encrypted section. See Avoid sending To/CC headers for verified groups. For opportunistic chats the main concern is how it affects other mail apps who might participate in chats.

Many other e-mail headers, in particular the “Subject” header, are end-to-end-encryption protected, see also this upcoming IETF RFC.

Yes. The best way is to send an Autocrypt Setup Message from the other e-mail client. Look for something like Start Autocrypt Setup Transfer in the settings of the other client and follow the instructions shown there.

Alternatively, you can import the key manually in “Settings” or “Advanced settings” and then “Import secret keys”. Caution: Make sure the key is not protected by a password, or remove the password beforehand.

If you don’t have a key or don’t even know you would need one - don’t worry: Delta Chat generates keys as needed, you don’t have to hit a button for it.

The most likely cause is that your key is encrypted and/or uses a password. Such keys are not supported by Delta Chat. You could remove the passphrase encryption and the password and try the import again. If you want to keep your passphrase you’ll have to create an e-mail alias for use with Delta Chat such that Delta Chat’s key is tied to this e-mail alias.

Delta Chat supports common OpenPGP private key formats, however, it is unlikely that private keys from all sources will be fully supported. This is not the main goal of Delta Chat. In fact, the majority of new users will not have any key prior to using Delta Chat. We do, however, try to support private keys from as many sources as possible.

Removing the password from the private key will depend on the software you use to manage your PGP keys. With Enigmail, you can set your password to an empty value in the Key Management window. With GnuPG you can set it via the command line. For other programs, you should be able to find a solution online.

Delta Chat uses the Autocrypt e2e-encryption standard. For a discussion of Autocrypt and pEp, see the Autocrypt FAQ.

If you want to use the same account on different devices, you should export a backup from the old device, and import it into the new device:

On the old device, go to “Settings” or “Settings / Chats and media” and then to “Backup”. Enter your screen unlock PIN, pattern, or password. Then you can click on “Start Backup”. This saves the backup file to your device. Now you have to transfer it to the other device somehow.

On the new device, on the login screen, instead of logging into your email account, choose “Import Backup”. After import, your conversations, encryption keys, and media should be copied to the new device.

You are now synchronized, and can use both devices for sending and receiving E2E-encrypted messages with your communication partners.

There are no immediate plans but some preliminary thoughts.

There are 2-3 avenues for introducing a Delta Chat Web Client, but all are significant work. For now, we focus on getting stable releases into all app stores (Google Play/iOS/Windows/macOS/Linux repositories) as native apps.

If you need a Web Client, because you are not allowed to install software on the computer you work with, you can use the portable Windows Desktop Client, or the AppImage for Linux. You can find them on get.delta.chat.

This is an experimental setting for some people who are experimenting with server-side rules. Not all providers support this, but with some you can move all mails with a “Chat-Version” header to the DeltaChat folder. Normally, this would be done by the Delta Chat app.

Watching the Inbox makes sense to turn off, if you have both:

• enabled a server-side rule to move all messages with Chat-Version header to the Delta Chat folder, and

have set the “Show classic emails” setting to “no, chats only”.

In this case, Delta Chat doesn’t need to watch the Inbox.

Sending a copy of your messages to yourself ensures that you receive your own messages on all devices. If you have multiple devices and don’t turn it on, you see only the messages from other people, and the messages you send from the current device.

The copy is sent to the Inbox, and then moved to the DeltaChat folder; it’s not put into the “Sent” folder. Delta Chat never uploads anything to the Sent folder because this would mean uploading a message twice (once through SMTP, and once through IMAP to Sent folder).

The default setting for copy-to-self is “no”.

The only reason one wants to watch the Sent folder is if you are using another mail program (like Thunderbird) next to your Delta Chat app, and want your MUA to participate in chat conversations.

However, we recommend using the Delta Chat Desktop Client; you can download it on get.delta.chat. The option to watch the “Sent” folder might go away in the future. It was introduced at a time where there was no Delta Chat Desktop client available on all platforms.

Some people use Delta Chat as a regular email client, and want to use the Inbox folder for their mail, instead of the DeltaChat folder. If you disable “Watch DeltaChat folder”, you should also disable “move chat messages to DeltaChat”. Otherwise, deleting messages or multi-device setups might not work properly.

With a rather good chance: Yes :) However, some providers need special options to work properly, see Provider Overview

Sending and receiving messages takes a few seconds, typically. Sometimes there are cases where it takes longer but that is arguably true as well for any other messenger.

Instant chatting works fast if both parties are actively using the app. It’s sometimes slower if the app is running in the background.

Receiving messages then can take minutes because both Android and iOS often stop Delta Chat from running in the background, and only wake it up occasionally. This artificial delay is usually worse on iOS than on Android. Note that Delta Chat doesn’t use Google Cloud Messaging (GCM) or the Apple Push Notification Service (APNS), because this leads to user tracking and central control which Delta Chat aims to avoid as much as feasible.

However, Android and iOS kill apps running in the background is a problem for many legitimate apps. For more information, see dontkillmyapp.com.

Yes and No.

No, you can not use your Protonmail, Tutanota, or Criptext account with Delta Chat; they do not offer receiving mails via IMAP.

In any case you can use Delta Chat to send Messages to people who use Protonmail, Tutanota, or Criptext. Those messages will not be End-to-End encrypted, though. The End-to-End encryption those providers offer is only working inside their platforms, and not compatible with anyone outside.

Delta Chat can e2e-encrypt through any e-mail provider with any Autocrypt-enabled e-mail app. I’m interested in the technical details. Can you tell me more? See Standards used in Delta Chat.

First of all, Delta Chat does not receive any Venture Capital and is not indebted, and under no pressure to produce huge profits, or to sell users and their friends and family to advertisers (or worse).

Delta Chat developments have so far been funded from four major sources:

1. The NEXTLEAP EU project funded the research and implementation of verified groups and setup contact protocols in 2017 and 2018.

1. The Open Technology Fund has given two grants. The first 2018/2019 grant (~$200K) majorly improved the Android app and allowed us to release a Desktop app beta version, and also moored our feature developments in UX research in human rights contexts, see our concluding Needfinding and UX report. The second 2019/2020 grant (~$300K) is still ongoing and helps us to release Delta/iOS versions, to convert our core library to Rust, and to provide new features for all platforms. See the ongoing blog posts for more info.

1. The NLnet foundation granted EUR 46K for completing Rust/Python bindings and instigating a Chat-bot ecosystem.

1. Last but by far not least, several pro-bono experts and enthusiasts contributed and contribute to Delta Chat developments without receiving money, or only small amounts. Without them, Delta Chat would not be where it is today, not even close.

The monetary funding mentioned above was organized by merlinux GmbH in Freiburg (Germany), and then distributed to almost a dozen contributors.

Funding for 2020/2021 is yet to be determined. We are pursuing several opportunities with different organizations and partners. We also are considering to ask for donations. In fact, we experimentally started a little Delta Chat / Liberapay donation account but have not published this yet. There were also around 3-4K so far donated to Bjoern’s (the original author of Delta Chat) paypal and bitcoin donation channels.

• adding technical details
• adding cross-links to developer sources (github)