Frequently Asked Questions

General
Groups
Encryption
Multi-client
Miscellaneous

General

What is Delta Chat?

Delta Chat is a new chat app that uses e-mails for transfering messages. If you receive a chat message just use your e-mail app to read the message and reply. You are not required to sign up anywhere, go to a website or install Delta Chat.

How can i find people to chat with?

With Delta Chat, you can write to every existing e-mail address - even if the recipient is not using the Delta Chat App. This is one of the biggest differences to other messengers: There is no need for the receiver to install the same app as yours.

What are the advantages of Delta Chat compared to other messengers?

Independent of any company or services. You own your data.
Your data are not saved on a central server; this way, in contrast to most other messengers, Delta Chat even protects your metadata (who writes to whom?)
You do not distribute your address book to anyone.
Fast by the use of Push-IMAP
Largest userbase - receivers 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
fully Open Source and Standards based

Which messages do appear in Delta Chat?

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. You can see the other messages in the main menu at Contact requests and, if desired, start a chat from there.

What about Spam?

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’s no spam.
However, if needed, you can block any contact.

Does Delta Chat support images, videos and other attachments?

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

Does Delta Chat support HTML-emails?

Yes. If incoming email lacks a plain text part, we convert HTML-emails to plain text ourselves. Outgoing emails always use plain text.

Groups

How can I create a group?

Select Add group from the “Sandwich menu” in the upper right corner of the chat overview.
On the following screen, select the group members and hit the check mark in the upper right corner. After that, you can define a group name.
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).

How to add members to a group?

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.

What is a verified group?

A “verified group” is an experimental feature (as of January 2019). By adding one another through QR-code scans a group of “verified” members can talk with each other. It enforces e2e group encryption that is safe against provider or network attacks. However, some user-tests and feedback suggests that UX and implementation changes makes sense. Recent discussions can be found here: https://countermitm.readthedocs.io/en/latest/new.html

I have deleted myself by accident.

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

I do not want to receive the messages of a group any longer.

Either delete yourself from the member list or delete the whole chat. If you want to join the group later again, ask another group member to add you again.
As an alternative, you can also “Mute” a group - doing so, you’ll get all messages and can still write but you’re no longer notified of any new messages.

Encryption

Does Delta Chat support end-to-end-encryption?

Yes. DeltaChat implements the Autocrypt Level 1 standard and can thus e2e-encrypt messages with other Autocrypt-capable apps.

What do I have to do to activate the end-to-end-encryption?

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 later messages are not encrypted until an Autocrypt-compliant app is available again.
If you want to deactivate the end-to-end-encryption, use the corresponding setting at “Settings / Advanced settings”.

If end-to-end-encryption is not available, is the connection not encrypted at all?

No. With most e-mail servers transport encryption (TLS) is used then.

How can I check the encryption?

If a little padlock is shown beside a message, this implies that the message is end-to-end-encrypted and is sent from the given sender and your answer will be end-to-end-encrypted as well.
If there is no padlock, the message is usually transported unencrypted eg. because you or the sender have disabled end-to-end-encryption or the sender uses an app that does not support end-to-end-encryption.

How can I verify the sender?

The user’s profile shows some additional information:

You can tap “QR Invite code” on Android and then use the “scan QR code” button on another device to scan this code. If both devices are online they will introduce a chat channel with each other (if it doesn’t exist already) and also the encryption keys will be verified.
For an end-to-end-encryption, Delta Chat shows two fingerprints there. If they are the same on the device of your chat partner, the connection is safe.
For transport encryption, this state is just shown there

Which standards are used for end-to-end-encryption?

OpenPGP. Key transport is done via Autocrypt.

Can I re-use my existing private key?

Yes. The best way is to send an Autocrypt Setup Message from the other e-mail client. Look for sth. 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 at “Advanced settings / Manage private keys”. Caution: Make sure, the key is not protected by a password or remove it before.

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

Multi-client

Can I use Delta Chat on multiple devices the same time?

If you want to use the same account on different (Autocrypt capable) devices, you have to synchronize their encryption capabilities:

On the first device, choose “Advanced settings / Send Autocrypt Setup message” and click until a “security number” is shown.
On the other device, wait for the “Autocrypt Setup Message” to arrive and click on it which should prompt you for the security number.
you are now successfully synchronized and can use both devices for sending and receiving e2e-encrypted messages with your communication partners.

Miscellaneous

Does Delta Chat work with my e-mail-provider?

With a rather good chance: Yes :)
However, some providers need special options to work properly; users have collected some of them in the forum at Provider Overview

I’m interested in the technical details. Can you tell me more?

See page Standards used in Delta Chat.