Preguntas Frecuentes

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¿Qué es Delta Chat?

Delta Chat is a reliable, decentralized and secure instant messaging app, available for mobile and desktop platforms.

How can I find people to chat with?

First, note that Delta Chat is a private messenger. There is no public discovery, you decide about your contacts.

Now wait while connection gets established.

Congratulations! You now will automatically use end-to-end encryption with this contact. If you add each other to groups, end-to-end encryption will be established among all members.

Why is a chat marked as “Request”?

As being a private messenger, only friends and family you share your QR code or invite link with can write to you.

Your friends may share your contact with other friends, this appears as a request.

How can I put two of my friends in contact with each other?

Attach the first contact to the chat of the second using Paperclip Attachment Button → Contact. You can also add a little introduction message.

The second contact will receive a card then and can tap it to start chatting with the first contact.

¿Delta Chat soporta envío de imágenes, videos, documentos y otros archivos?

¿Qué son los perfiles? ¿Cómo puedo cambiar entre ellos?

A profile is a name, a picture and some additional information for encrypting messages. A profile lives on your device(s) only and uses the server only to relay messages.

En la primera instalación de Delta Chat se crea un primer perfil.

Después, puedes tocar la imagen de tu perfil en la esquina superior izquierda para Añadir perfiles o para Cambiar perfiles.

You may want to use separate profiles for political, family or work related activities.

Quizás quieres aprender cómo se usa el mismo perfil en múltiples dispositivos.

¿Quién ve mi foto de perfil?

Can I set a Bio/Status with Delta Chat?

Yes, you can do so under Settings → Profile → Bio. Once you sent a message to a contact, they will see it when they view your contact details.

¿Qué significa fijar, mutear, archivar?

Usa estas herramientas para organizar tus chats y mantener todo en su lugar:

Para archivar o fijar un chat, toque prolongadamente (Android), use el menú del chat (Android/Escritorio) o deslícese hacia la izquierda (iOS); para silenciar un chat, use el menú del chat (Android/Escritorio) o el perfil del chat (iOS).

¿Cómo funcionan los “Mensajes guardados”?

Mensajes guardados es un chat que puedes utilizar para recordar y encontrar mensajes fácilmente.

Los mensajes se quedan guardados, también si se han cambiado o están borrados - Sea por el remitente, por la limpieza del dispositivo o por la desaparición de mensajes de otros chats.

¿Qué significa el punto verde?

You can sometimes see a green dot next to the avatar of a contact. It means they were recently seen by you in the last 10 minutes, e.g. because they messaged you or sent a read receipt.

So this is not a real time online status and others will as well not always see that you are “online”.

¿Qué significan las marcas que se muestran junto a los mensajes salientes?

Corregir errores y borrar mensajes después de enviar

Mientras que los mensajes editados tendrán la palabra “Editado” junto a la marca de tiempo, los mensajes borrados serán eliminados sin un marcador en el chat. No se envían notificaciones y no hay límite de tiempo.

Note, that the original message may still be received by chat members who could have already replied, forwarded, saved, screenshotted or otherwise copied the message.

¿Cómo funciona la desaparición de mensajes?

You can turn on “disappearing messages” in the settings of a chat, at the top right of the chat window, by selecting a time span between 5 minutes and 1 year.

Until the setting is turned off again, each chat member’s Delta Chat app takes care of deleting the messages after the selected time span. The time span begins when the receiver first sees the message in Delta Chat. The messages are deleted both, on the servers, and in the apps itself.

Tenga en cuenta que puede confiar en los mensajes que desaparecen sólo mientras confíes en tus compañeros de chat; compañeros de chat maliciosos pueden tomar fotos, o guardar, copiar o reenviar mensajes antes de eliminarlos.

Apart from that, if one chat partner uninstalls Delta Chat, the (anyway encrypted) messages may take longer to get deleted from their server.

¿Qué pasa si activo “Borrar mensajes del dispositivo”?

How can I delete my chat profile?

If you are using more than one chat profile, you can remove single ones in the top profile switcher menu (on Android and iOS), or in the sidebar with a right click (in the Desktop app). Chat profiles are only removed on the device where deletion was triggered. Chat profiles on other devices will continue to fully function.

If you use a single default chat profile you can simply uninstall the app. This will still automatically trigger deletion of all associated address data on the chatmail server. For more info, please refer to nine.testrun.org address-deletion or the respective page from your chosen 3rd party chatmail server.

Groups

Groups let several people chat together privately with equal rights.

Anyone can change the group name or avatar, add or remove members, set disappearing messages, and delete their own messages from all member’s devices.

Because all members have the same rights, groups work best among trusted friends and family.

Creación de un grupo

Add and remove members

QR code and invite link can be used to add several members. However, since groups are meant for trusted people, avoid sharing them publicly.

Me he eliminado por accidente.

No quiero recibir más los mensajes de un grupo.

Cloning a group

You can duplicate a group to start a separate discussion or to exclude members without them noticing.

The new group is fully independent from the original, which continues to work as before.

In-chat apps

You can send apps to a chat - games, editors, polls and other tools. This makes Delta Chat a truly extensible messenger.

Where can I get in-chat apps?

How private are in-chat apps?

How can I create my own in-chat apps?

Entrega de mensajes instantáneos y notificaciones Push

¿Qué son las Notificaciones Push? ¿Cómo puedo recibir mensajes instantáneos?

Push Notifications are sent by Apple and Google “Push services” to a user’s device so that an inactive Delta Chat app can fetch messages in the background and show notifications on a user’s phone if needed.

Las notificaciones push funcionan con todos los servidores de chatmail en

¿Están activadas las notificaciones Push en los dispositivos iOS? ¿Existe alguna alternativa?

Yes, Delta Chat automatically uses Push Notifications for chatmail profiles. And no, there is no alternative on Apple’s phones to achieve instant message delivery because Apple devices do not allow Delta Chat to fetch data in the background. Push notifications are automatically activated for iOS users because Delta Chat’s privacy-preserving Push Notification system does not expose data to Apple that it doesn’t already have.

¿Están habilitadas / son necesarias las notificaciones Push en los dispositivos Android?

If a “Push Service” is available, Delta Chat enables Push Notifications to achieve instant message delivery for all chatmail users.

In the Delta Chat “Notifications” settings for “Instant delivery” you can change the following settings effecting all chat profiles:

Both “Background Connection” options are energy-efficient and safe to try if you experience messages arrive only with long delays.

¿Qué privadas son las notificaciones push de Delta Chat?

Delta Chat Push Notification support avoids leakage of private information. It does not leak profile data, IP address or message content (not even encrypted) to any system involved in the delivery of Push Notifications.

Así es como las aplicaciones Delta Chat realizan la entrega de Notificaciones Push:

The central Delta Chat notification proxy is small and fully implemented in Rust and forgets about device-tokens as soon as Apple/Google/etc processed them, usually in a matter of milliseconds.

Note that the device token is encrypted between apps and notification proxy but it is not signed. The notification proxy thus never sees profile data, IP-addresses or any cryptographic identity information associated with a user’s device (token).

Resulting from this overall privacy design, even the seizure of a chatmail server, or the full seizure of the central Delta Chat notification proxy would not reveal private information that Push services do not already have.

Why does Delta Chat integrate with centralized proprietary Apple/Google push services?

Delta Chat is a free and open source decentralized messenger with free server choice, but we want users to reliably experience “instant delivery” of messages, like they experience from WhatsApp, Signal or Telegram apps, without asking questions up-front that are more suited to expert users or developers.

Note that Delta Chat has a small and privacy-preserving Push Notification system that achieves “instant delivery” of messages for all chatmail servers including a potential one you might setup yourself without our permission. Welcome to the power of the interoperable chatmail relay network :)

Múltiples dispositivos

¿Puedo usar Delta Chat en varios dispositivos al mismo tiempo?

Yes. You can use the same profile on different devices:

A diferencia de muchas otras aplicaciones de mensajería, después de una transferencia exitosa, ambos dispositivos son completamente independientes. No es necesario un dispositivo para que el otro funcione.

Solución de problemas

Transferencia manual

This method is only recommended if “Add Second Device” as described above does not work.

¿Tienen planeado crear un cliente web de Delta Chat?

Advanced

Experimental Features

At Settings → Advanced → Experimental Features you can try out features we are working on.

The features may be unstable and may be changed or removed.

You can find more information and give feedback in the Forum.

What is “Send statistics to Delta Chat’s developers”?

We would like to improve Delta Chat with your help, which is why Delta Chat for Android asks whether you want to send anonymous usage statistics.

You can turn it on and off at Settings → Advanced → Send statistics to Delta Chat’s developers.

When you turn it on, weekly statistics will be automatically sent to a bot.

We are interested e.g. in statistics like:

We will not collect any personally identifiable information about you.

Can I use a classic email address with Delta Chat?

Yes, but only if the email address is used exclusively by chatmail clients.

It is not supported to share usage of an email address with non-chatmail apps or web-based mailers, for the following reasons:

How can I configure a chat profile with a classic email address as transport?

First off, please do not use the same classic email address also from non-chatmail classic email apps unless you are prepared to deal with encrypted messages in the inbox, double notifications, accidentally deleted emails or similar annoyances.

You can configure a email address for chatting at New Profile → Use Other Server → Use Classic Mail as Transport. Note that classic email providers will generally not support Push Notifications and have other limitations, see Provider Overview. Chatmail uses the default INBOX for relay; ensure the provider setup does too. A chat profile using a classic email address allows to to send and receive unencrypted messages. These messages, and the chats they appear in, are marked with an email icon email.

I want to manage my own server for Delta Chat. What do you recommend?

Any well behaving email server setup will do fine except if your users’ devices require Google/Apple Push Notifications to work properly.

We generally recommend to set up a chatmail relay. Chatmail is a community-driven project that encompasses both the setup of relays and core Rust developments that power chatmail clients of which Delta Chat is the most well known.

Estoy interesado en los detalles técnicos. ¿Pueden decirme más?

Cifrado y seguridad

¿Qué estándares se utilizan para el cifrado de extremo a extremo?

Delta Chat uses a secure subset of the OpenPGP standard to provide automatic end-to-end encryption using these protocols:

Delta Chat does not query, publish or interact with any OpenPGP key servers.

How can I know if messages are end-to-end encrypted?

All messages in Delta Chat are end-to-end encrypted by default. Since the Delta Chat Version 2 release series (July 2025) there are no lock or similar markers on end-to-end encrypted messages, anymore.

Can I still receive or send messages without end-to-end encryption?

If you use default chatmail relays, it is impossible to receive or send messages without end-to-end encryption.

If you instead use a classic email server, you can send and receive messages with or without end-to-end encryption. Messages lacking end-to-end encryption are marked with an email icon email.

What does the green checkmark in a contact profile mean?

A contact profile might show a green checkmark green checkmark and an “Introduced by” line. Every green-checkmarked contact either did a direct QR-scan with you or was introduced by a another green-checkmarked contact. Introductions happen automatically when adding members to groups. Whoever adds a green-checkmarked contact to a group with only green-checkmarked members becomes an introducer. In a contact profile you can tap on the “Introduced by …” text repeatedly until you get to the one with whom you directly did a QR-scan.

Para obtener una discusión más detallada sobre “cifrado de extremo a extremo garantizado”, por favor consulta los protocolos Secure-Join y lee específicamente sobre “Grupos Verificados”, el término técnico de lo que aquí se llama chats “marcados con una estampilla verde” o “cifrados de extremo a extremo garantizado”.

¿Los adjuntos (imágenes, archivos, audio, etc.) están cifrados de extremo a extremo?

Yes.

Cuando hablamos de un mensaje “cifrado de extremo a extremo”, siempre nos referimos a que todo el mensaje está cifrado, incluyendo todos los archivos adjuntos y los metadatos de los archivos adjuntos, como los nombres de archivo.

¿Es OpenPGP seguro?

Yes, Delta Chat uses a secure subset of OpenPGP requiring the whole message to be properly encrypted and signed. For example, “Detached signatures” are not treated as secure.

OpenPGP is not insecure by itself. Most publicly discussed OpenPGP security problems actually stem from bad usability or bad implementations of tools or apps (or both). It is particularly important to distinguish between OpenPGP, the IETF encryption standard, and GnuPG (GPG), a command line tool implementing OpenPGP. Many public critiques of OpenPGP actually discuss GnuPG which Delta Chat has never used. Delta Chat rather uses the OpenPGP Rust implementation rPGP, available as an independent “pgp” package, and security-audited in 2019 and 2024.

We aim, along with other OpenPGP implementors, to further improve security characteristics by implementing the new IETF OpenPGP Crypto-Refresh which was thankfully adopted in summer 2023.

Did you consider using alternatives to OpenPGP for end-to-end-encryption?

Yes, we are following efforts like MLS but adopting them would mean breaking end-to-end encryption interoperability. So it would not be a light decision to take and there must be tangible improvements for users.

Delta Chat takes a holistic “usable security” approach and works with a wide range of activist groupings as well as renowned researchers such as TeamUSEC to improve actual user outcomes against security threats. The wire protocol and standard for establishing end-to-end encryption is only one part of “user outcomes”, see also our answers to device-seizure and message-metadata questions.

¿Es Delta Chat vulnerable a EFAIL?

No, Delta Chat never was vulnerable to EFAIL because its OpenPGP implementation rPGP uses Modification Detection Code when encrypting messages and returns an error if the Modification Detection Code is incorrect.

Delta Chat also never was vulnerable to the “Direct Exfiltration” EFAIL attack because it only decrypts multipart/encrypted messages which contain exactly one encrypted and signed part, as defined by the Autocrypt Level 1 specification.

Are messages marked with the mail icon exposed on the Internet?

If you are sending or receiving email messages without end-to-end encryption (using a classic email server), they are still protected from cell or cable companies who can not read or modify your email messages. But both your and your recipient’s email providers may read, analyze or modify your messages, including any attachments.

Delta Chat by default uses strict TLS encryption which secures connections between your device and your email provider. All of Delta Chat’s TLS-handling has been independently security audited. Moreover, the connection between your and the recipient’s email provider will typically be transport-encrypted as well. If the involved email servers support MTA-STS then transport encryption will be enforced between email providers in which case Delta Chat communications will never be exposed in cleartext to the Internet even if the message was not end-to-end encrypted.

¿Cómo Delta Chat protege los metadatos en los mensajes?

Unlike most other messengers, Delta Chat apps do not store any metadata about contacts or groups on servers, also not in encrypted form. Instead, all group metadata is end-to-end encrypted and stored on end-user devices, only.

Servers can therefore only see:

By default, the addresses are randomly generated.

All other message, contact and group metadata resides in the end-to-end encrypted part of messages.

¿Cómo proteger los metadatos y los contactos cuando se incauta un dispositivo?

Both for protecting against metadata-collecting servers as well as against the threat of device seizure we recommend to use a chatmail relay to create chat profiles using random addresses for transport. Note that Delta Chat apps on all platforms support multiple profiles so you can easily use situation-specific profiles next to your “main” profile with the knowledge that all their data, along with all metadata, will be deleted. Moreover, if a device is seized then chat contacts using short-lived profiles can not be identified easily.

Does Delta Chat support “Sealed Sender”?

No, not yet.

The Signal messenger introduced “Sealed Sender” in 2018 to keep their server infrastructure ignorant of who is sending a message to a set of recipients. It is particularly important because the Signal server knows the mobile number of each account, which is usually associated with a passport identity.

Even if chatmail relays do not ask for any private data (including no phone numbers), it might still be worthwhile to protect relational metadata between addresses. We don’t foresee bigger problems in using random throw-away addresses for sealed sending but an implementation has not been agreed as a priority yet.

¿Soporta Delta Chat Perfect Forward Secrecy?

No, not yet.

Delta Chat today doesn’t support Perfect Forward Secrecy (PFS). This means that if your private decryption key is leaked, and someone has collected your prior in-transit messages, they will be able to decrypt and read them using the leaked decryption key. Note that Forward Secrecy only increases security if you delete messages. Otherwise, someone obtaining your decryption keys is typically also able to get all your non-deleted messages and doesn’t even need to decrypt any previously collected messages.

We designed a Forward Secrecy approach that withstood initial examination from some cryptographers and implementation experts but is pending a more formal write up to ascertain it reliably works in federated messaging and with multi-device usage, before it could be implemented in chatmail core, which would make it available in all chatmail clients.

Does Delta Chat support Post-Quantum-Cryptography?

No, not yet.

Delta Chat uses the Rust OpenPGP library rPGP which supports the latest IETF Post-Quantum-Cryptography OpenPGP draft. We aim to add PQC support in chatmail core after the draft is finalized at the IETF in collaboration with other OpenPGP implementers.

How can I manually check encryption information?

Puede verificar manualmente el estado de cifrado de extremo a extremo en el diálogo “Cifrado” (perfil de usuario en Android/iOS o hacer clic derecho en el elemento de lista de chat de un usuario en el escritorio). Delta Chat muestra dos huellas digitales allí. Si las mismas huellas digitales aparecen en su propio dispositivo y en el dispositivo de su contacto, la conexión es segura.

¿Puedo reutilizar mi clave privada existente?

No.

Delta Chat generates secure OpenPGP keys according to the Autocrypt specification 1.1. We do not recommend or offer users to perform manual key management. We want to ensure that security audits can focus on a few proven cryptographic algorithms instead of the full breadth of possible algorithms allowed with OpenPGP. If you want to extract your OpenPGP key, there only is an expert method: you need to look it up in the “keypairs” SQLite table of a profile backup tar-file.

¿Se auditó Delta Chat de forma independiente en busca de vulnerabilidades de seguridad?

Yes, multiple times. The Delta Chat project continuously undergoes independent security audits and analysis, from most recent to older:

Miscelaneo

¿Qué permisos necesita Delta Chat?

Some features require certain permissions, e.g. you need to grant camera permission if you want to scan an invite QR code.

See Privacy Policy for a detailed overview.

Where can my friends find Delta Chat?

Delta Chat is available for all major and some minor platforms:

¿Cómo se financia el desarrollo de Delta Chat?

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). We rather use public funding sources, so far from EU and US origins, to help our efforts in instigating a decentralized and diverse chat messaging eco-system based on Free and Open-Source community developments.

Concretely, Delta Chat developments have so far been funded from these sources, ordered chronologically:

La financiación monetaria mencionada anteriormente es principalmente organizada por merlinux GmbH en Freiburg (Alemania), y se distribuye a más de una docena de colaboradores en todo el mundo.

Por favor, consulta Canales de contribución de Delta Chat para conocer las posibilidades de contribución tanto monetarias como otras.