- O que é o Delta Chat
  - Como posso encontrar pessoas para conversar?
  - Por que um chat está marcado como “Solicitação”?
  - Como posso colocar dois dos meus amigos em contato um com o outro?
  - O que são perfis? Como posso alternar entre eles?
  - Quem consegue ver a imagem do meu perfil?
  - Posso definir uma Bio/Assinatura com o Delta Chat?
  - O que significa Fixar, Silenciar e Arquivar?
  - Como funcionam as “Mensagens salvas”?
  - O que significa o ponto verde?
  - O que significam os carrapatos mostrados ao lado das mensagens de saída?
  - Corrigir erros de digitação e excluir mensagens após o envio
  - How is media quality handled?
  - Como funcionam as mensagens efêmeras?
  - O que acontece se eu ativar a opção “Apagar mensagens do dispositivo”?
  - Como posso excluir minha conta?
- Grupos
  - Criação de um grupo
  - Adicionar e remover membros
  - Deletei minha própria conta por acidente.
  - Não quero mais receber as mensagens de um grupo.
  - Clonagem de grupos
  - Quantos membros podem participar em um único grupo?
- Channels
  - Subscribe to a channel
  - Create a channel
  - How many subscribers can a channel have?
- Calls
  - Place a call
  - Accept or reject a call
  - During a call
  - Missed calls and notifications
- Aplicativos embutidos
  - Onde posso obter aplicativos embutidos?
  - How private are in-chat apps?
  - How can I create my own in-chat apps?
- Instant message delivery and Push Notifications
  - What are Push Notifications? How can I get instant message delivery?
  - Are Push Notifications enabled on iOS devices? Is there an alternative?
  - Are Push notifications enabled / needed on Android devices?
  - How private are Delta Chat Push Notifications?
  - Why does Delta Chat integrate with centralized proprietary Apple/Google push services?
- Multi-cliente
  - Posso usar o Delta Chat em vários dispositivos ao mesmo tempo?
  - Troubleshooting
  - Manual Transfer
  - Existe algum plano para a introdução de um cliente Web para Delta Chat?
- Advanced
  - Experimental Features
  - What are Relays?
  - Can I use a classic email address with Delta Chat?
  - How can I configure a chat profile with a classic email address as relay?
  - I want to manage my own server for Delta Chat. What do you recommend?
  - What is “Send statistics to Delta Chat’s developers”?
  - Estou interessado nos detalhes técnicos. Pode me dizer mais?
- Encryption and Security
  - Which standards are used for end-to-end encryption?
  - How can I know if messages are end-to-end encrypted?
  - Can I still receive or send messages without end-to-end encryption?
  - What does the green checkmark in a contact profile mean?
  - Are attachments (pictures, files, audio etc.) end-to-end encrypted?
  - Is OpenPGP secure?
  - Did you consider using alternatives to OpenPGP for end-to-end-encryption?
  - Is Delta Chat vulnerable to EFAIL?
  - Are messages marked with the mail icon exposed on the Internet?
  - How does Delta Chat protect metadata in messages?
  - How to protect metadata and contacts when a device is seized?
  - Who sees my IP Address?
  - Does Delta Chat support “Sealed Sender”?
  - Does Delta Chat support Perfect Forward Secrecy?
  - Does Delta Chat support Post-Quantum-Cryptography?
  - How can I manually check encryption information?
  - Posso reutilizar minha chave privada existente?
  - Was Delta Chat independently audited for security vulnerabilities?
- Diverso
  - Quais permissões o Delta Chat precisa?
  - Where can my friends find Delta Chat?
  - Como são os desenvolvimentos do Delta Chat financiados?

## O que é o Delta Chat

Delta Chat é um aplicativo de mensagens instantâneas confiável, descentralizado e seguro, disponível para desktop e plataformas móveis.

- Criação instantânea de **perfis de chat privados ** com relays chatmail seguros e interoperáveis que oferecem entrega de mensagens instantâneas e Notificações Push para dispositivos iOS e Android.

- Suporte a vários perfis e a vários dispositivos em todas as plataformas e entre diferentes aplicativos de chatmail.

- Aplicativos interativos embutidos para jogos e colaboração

- Criptografia de ponta a ponta auditada segura contra ataques à rede e ao servidor.

- Software gratuito e de código aberto, tanto no aplicativo quanto no servidor, desenvolvido com base nos Padrões da Internet.

### Como posso encontrar pessoas para conversar?

Primeiro, observe que o Delta Chat é um mensageiro privado. Não há descoberta pública, você decide sobre seus contatos.

- Se você estiver cara a cara com seu amigo ou parente, toque no ícone de QR Code na tela principal.
  Peça ao seu parceiro para escanear o QR code com o aplicativo Delta Chat dele.

- Para criar um contato remotamente, na mesma tela, clique em “Copiar” ou “Compartilhar” e envie o link do convite por meio de outro mensageiro privado.

Agora, aguarde enquanto a conexão se estabelece.

- Se ambos os lados estiverem on-line, vocês logo verão um chat e poderão começar a enviar mensagens com segurança.

- Se um lado estiver off-line ou em uma rede ruim, a capacidade de acessar o chat será atrasada até que a conectividade seja restaurada.

Parabéns! Agora você usará automaticamente a criptografia de ponta a ponta com esse contato. Se vocês se adicionarem a grupos, a criptografia de ponta a ponta será estabelecida entre todos os membros.

### Por que um chat está marcado como “Solicitação”?

Por ser um mensageiro privado, somente amigos e familiares com quem você compartilha seu QR code ou link de convite podem escrever para você.

Seus amigos podem compartilhar seu contato com outros amigos, isso aparece como Solicitação

- Você precisa aceitar a solicitação antes de poder responder.

- Você também pode excluir a solicitação se não quiser conversar com a pessoa por enquanto.

- Se você excluir uma solicitação, as mensagens futuras desse contato ainda aparecerão como solicitação de mensagem, assim você pode mudar de ideia. Se você realmente não quiser receber mensagens dessa pessoa, considere bloqueá-la.

### Como posso colocar dois dos meus amigos em contato um com o outro?

Anexe o primeiro contato ao chat do segundo clicando em Botão de Anexo → Contato. Você também pode adicionar uma pequena mensagem de apresentação.

O segundo contato receberá um cartão e poderá tocar nele para começar a conversar com o primeiro contato.

### O que são perfis? Como posso alternar entre eles?

Um perfil é um nome, uma foto e algumas informações adicionais para criptografar mensagens. Um perfil reside apenas em seu(s) dispositivo(s) e usa o servidor somente para transportar mensagens.

Na primeira instalação do Delta Chat, é criado um primeiro perfil.

Depois, você pode tocar em sua imagem de perfil no canto superior esquerdo para Adicionar Conta ou para Mudar de Conta.

Talvez você queira usar perfis separados para atividades políticas, familiares ou atividades do trabalho.

Talvez você também queira aprender como usar a mesma conta em vários dispositivos.

### Quem consegue ver a imagem do meu perfil?

Você pode adicionar uma imagem de perfil nas suas configurações. Se você escrever aos seus contatos ou adicioná-los via código QR, eles automaticamente verão a imagem do seu perfil.

Por motivos de privacidade, ninguém pode ver a imagem do seu ṕerfil até que você escreva para as pessoas.

### Posso definir uma Bio/Assinatura com o Delta Chat?

Sim, você pode fazer isso em Configurações → Conta → Assinatura. Depois de enviar uma mensagem para um contato, ele verá sua assinatura quando visualizar seus detalhes de contato.

### O que significa Fixar, Silenciar e Arquivar?

Use essas ferramentas para organizar seus chats e manter tudo em seu devido lugar:

- Os chats fixados sempre ficam no topo da lista de conversas. Você pode usá-los para acessar seus chats mais queridos rapidamente ou temporariamente para não se esquecer de nada.

- Silencie os chats se não quiser receber notificações deles. Os bate-papos silenciados permanecem no lugar e você também pode fixar um chat silenciado.

- Arquive chats se não quiser mais vê-los em sua lista de conversas. Eles permanecem acessíveis acima da lista conversa ou por meio de pesquisa e são marcados como Arquivado

- Quando um chat arquivado receber uma nova mensagem, a menos que esteja silenciado, ele sairá do arquivo e voltará à sua lista de conversas. Os chats silenciados permanecem arquivados até que você os desarquive manualmente.

Para usar as funções, toque e segure ou clique com o botão direito do mouse em um conversa na lista conversas.

### Como funcionam as “Mensagens salvas”?

Saved Messages é um chat que você pode usar para lembrar e localizar facilmente as mensagens.

- Em qualquer chat, dê um toque longo ou clique com o botão direito do mouse em uma mensagem e selecione Salvar

- As mensagens salvas são marcadas com o símbolo ao lado do registro de data e hora

- Depois, abra o chat de “Mensagens salvas” - e você verá as mensagens salvas lá. Ao tocar em , você pode voltar para a mensagem original no chat original

- Por fim, você também pode usar “Mensagens Salvas” para fazer notas pessoais - abra o chat, digite algo, adicione uma foto ou uma mensagem de voz etc.

- Como as “Mensagens salvas” são sincronizadas, elas podem se tornar muito úteis para a transferência de dados entre dispositivos

As mensagens permanecem salvas mesmo que sejam editadas ou excluídas - seja pelo remetente, por limpeza do dispositivo ou por mensagens temporárias de outros chats.

### O que significa o ponto verde?

Às vezes, você pode ver um ponto verde ao lado do avatar de um contato. Isso significa que ele foi visto recentemente por você nos últimos 10 minutos, por exemplo, porque ele enviou uma mensagem para você ou uma confirmação de leitura.

Portanto, essa não é uma checagem de status on-line em tempo real e outras pessoas também nem sempre verão que você está “on-line”.

### O que significam os carrapatos mostrados ao lado das mensagens de saída?

- Um tique significa que a mensagem foi enviada com sucesso para o relay.

- Dois ticks** indicam que seu contato leu a mensagem.

Em grupos, o segundo tique significa que pelo menos um membro leu a mensagem.

Você só receberá o segundo tique se tanto você quanto um dos destinatários que leu a mensagem tiverem Configurações → Conversas → Confirmação de leitura ativada.

### Corrigir erros de digitação e excluir mensagens após o envio

- Você pode editar o texto de suas mensagens após o envio. Para isso, toque longamente ou clique com o botão direito do mouse na mensagem e selecione Editar Mensagem ou .

- Se você tiver enviado uma mensagem acidentalmente, no mesmo menu, selecione Apagar e, em seguida, Apagar para Toda a Gente.

Enquanto as mensagens editadas terão a palavra “Editado” ao lado do registro de data e hora, as mensagens excluídas serão removidas sem um marcador no chat. Não são enviadas notificações e não há limite de tempo.

Observe que a mensagem original ainda pode ser recebida pelos membros do conversa que podem ter respondido, encaminhado, salvo, capturado a tela ou copiado a mensagem.

### How is media quality handled?

Imagens, vídeos, arquivos, mensagens de voz etc. podem ser enviados usando os botões de Anexo- ou Mensagem de Voz

- By default, compression ensures fast, efficient delivery that respects everyone’s data limits and storage. This is ideal for everyday communication.

- In regions with worse connectivity, you can choose higher compression at Settings → Chats → Outgoing Media Quality.

- If you specifically need to send media in its original quality, use Attach → File in the chat. Please use this method sparingly, as sending original files will significantly increase data usage for you and all recipients in the chat.

### Como funcionam as mensagens efêmeras?

Você pode ativar a opção “mensagens temporárias” nas configurações de um conversa, no canto superior direito da janela conversa, selecionando um intervalo de tempo entre 5 minutos e 1 ano.

Até que a configuração seja desativada novamente, o aplicativo Delta Chat de cada membro do conversa se encarrega de de excluir as mensagens após o período de tempo selecionado. O intervalo de tempo começa quando o destinatário vê a mensagem pela primeira vez no Delta Chat. As mensagens são excluídas tanto nos servidores como nos próprios aplicativos.

Observe que você pode confiar no desaparecimento das mensagens somente se você confiar em seus parceiros do conversa; parceiros mal-intencionados de conversa podem tirar fotos, ou salvar, copiar ou encaminhar mensagens antes de excluí-las.

Além disso, se um parceiro de conversa desinstalar o Delta Chat, as mensagens (de qualquer forma criptografadas) podem demorar mais para serem excluídas do servidor deles.

### O que acontece se eu ativar a opção “Apagar mensagens do dispositivo”?

Se quiser economizar espaço de armazenamento no dispositivo, você pode optar por excluir mensagens antigas automaticamente.

Para ativá-la, vá para Configurações → Conversas → Apagar mensagens do dispositivo. Você pode definir um período de tempo entre “após uma hora” e “após um ano”; Dessa forma, todas as mensagens serão excluídas de seu dispositivo assim que forem mais antigas do que isso.

### Como posso excluir minha conta?

Se estiver usando mais de uma conta, você pode removê-las individualmente no menu superior de mudar de conta (no Android e no iOS), ou na barra lateral com um clique no botão direito do mouse (no aplicativo para desktop). As contas são removidas somente no dispositivo em que a exclusão foi acionada. Contas em outros dispositivos continuarão funcionando plenamente.

Se você usar uma conta única padrão, poderá simplesmente desinstalar o aplicativo. Isso ainda acionará automaticamente a exclusão de todos os dados de endereço associados no servidor de chatmail. Para obter mais informações, consulte nine.testrun.org address-deletion ou a respectiva página do servidor de chatmail de terceiros que você escolheu.

## Grupos

Os grupos permitem que várias pessoas conversem em particular com direitos iguais.

Qualquer pessoa pode alterar o nome do grupo ou o avatar, adicionar ou remover membros, definir mensagens temporárias, e excluir suas próprias mensagens dos dispositivos de todos os membros.

Como todos os membros têm os mesmos direitos, os grupos funcionam melhor entre amigos e familiares de confiança.

### Criação de um grupo

- Selecione Nova Conversa e em seguida Novo Grupo no menu que fica na parte de cima da tela, no canto direito, ou clique no botão correspondente no ANdroid/iOS.

- Na tela seguinte, selecione os membros do grupo e defina o nome do grupo. Você também pode selecionar o avatar do grupo (uma imagem).

- Logo após você escrever a primeira mensagem, todas as pessoas do grupo serão informadas sobre o novo grupo e poderão responder no grupo (a não que você escreva uma mensagem ali, o grupo estará invisível para os membros).

### Adicionar e remover membros

Todos os membros do grupo têm os mesmos direitos. Por este motivo, todos podem remover qualquer membro ou adicionar novos membros.

- Para adicionar ou remover membros, toque no nome do grupo dentro do chat e selecione o membro a adicionar ou a remover.

- Se o membro ainda não estiver na sua lista de contactos, mas estiver cara a cara com você, na mesma tela, moste um QR code.
  Peça ao seu parceiro de conversa para escanear o QR code com o Delta Chat dele, tocando em na tela inicial.

- Para adicionar um membro remotamente, clique em “Copiar” ou “Compartilhar” e envie o link do convite por meio de outro mensageiro privado para o novo membro.

O QR code e o link de convite podem ser usados para adicionar vários membros. No entanto, como os grupos são destinados a pessoas de confiança, evite compartilhá-los publicamente.

### Deletei minha própria conta por acidente.

Já que você não é mais um membro do grupo, não tem como se adicionar novamente. Entretanto, não tem problema, é só pedir para outra pessoa do grupo, através de um chat normal, adicionar você.

### Não quero mais receber as mensagens de um grupo.

- Ou você se exclui do grupo ou apaga a conversa inteira do grupo. Se você quiser entrar mais tarde no grupo novamente, peça a outra pessoa do grupo para adicioná-la novamente.

Uma alternativa é “silenciar” um grupo. Fazendo isso, você receberá todas as mensagens e ainda poderá escrever, mas não será receberá mais notificações d enovas mensagens.

### Clonagem de grupos

Você pode duplicar um grupo para iniciar uma discussão separada ou para excluir membros sem que eles percebam.

- Abra o perfil do grupo e toque em Clonar conversa (Android/iOS), ou clique com o botão direito do mouse no grupo na lista de conversa (desktop).

- Defina um novo nome, escolha um avatar e ajuste a lista de membros, se necessário.

O novo grupo é totalmente independente do original, que continua funcionando como antes.

### Quantos membros podem participar em um único grupo?

Não há um limite técnico rigoroso, mas não é recomendável mais de 150.

À medida que os grupos se tornam maiores, eles podem se tornar socialmente instáveis e podem precisar de uma hierarquia - mas o Delta Chat é um mensageiro privado para conversar com direitos iguais. Consulte o Número de Dunbar para obter mais informações.

## Channels

Channels are a one-to-many tool for broadcasting messages.

### Subscribe to a channel

- Scan the QR code or tap the invite link you got from the channel owner.

That’s all! You will receive a few of the messages from the channel history and, from that point on, all new messages from the channel.

Don’t worry, if that does not happen immediately. Once the channel owner comes online, your join request will be processed.

As all of Delta Chat, also Channels are private and decentralized, there is no public discovery.

Other channel subscribers will not see that you subscribed and cannot message you. The channel owner, however, can message you. They will also see that you read a message unless you have read receipts disabled.

If you do not want to share your main profile, you can also create a dedicated profile for joining a channel.

### Create a channel

- Tap New Chat and choose New Channel.

- Enter a name, optionally set an image and description, and hit the Create button.

- You can now send and manage messages as usual.

- From the channel’s profile, share the QR code or invite link with others.

Subscribers will receive your messages, but they cannot send messages in your channel. When subscribing, they will receive a few of the latest messages of the channel history.

You can see the view count beside each message. Note that this only counts subscribers who have read receipts enabled, so the real view count may be larger.

### How many subscribers can a channel have?

Channels are designed for much larger audiences than groups.

The practical limit depends on the used relay, so there is no single fixed number that applies everywhere.

For really large channels with several tens of thousands of subscribers, we recommend using a dedicated profile for the channel and checking whether the relay is suitable.

But don’t be too hesitant: Delta Chat is designed to be relay-agnostic, so you can change your relay at any point easily - your existing subscribers will not even notice. You only have to update the invite link you share with new subscribers in that case.

## Calls

Delta Chat supports one-to-one audio calls and video calls.

Calls are supported on Desktop, Ubuntu Touch, iOS and Android 8 and newer.

### Place a call

- In a one-to-one chat, tap the 📞 call icon.

- This opens a small menu where you can choose whether to place an Audio Call or a Video Call.

### Accept or reject a call

- When someone calls you, Delta Chat shows an incoming call screen or notification.

- Tap Accept to answer or Decline to reject the call.

### During a call

- You can mute your microphone.

- You can enable or disable your camera.

- On mobile, you can switch between front and back cameras.

Depending on the device, you can also select the audio output or use picture-in-picture. On desktop, the call is using a dedicated window and you can continue using the main Delta Chat window as usual.

### Missed calls and notifications

- If you do not answer, do not hear the ringing, or do not have your device at hand, the call appears as a missed call.

- Only your accepted contacts can make your device ring. Contact requests will appear as usual and will not ring.

- At Settings → Notifications → Calls, you can disable the special call ringing screen completely. If you do so, you will not be disturbed by any ringing notification, you can still pick up the call by tapping the incoming call message bubble in its chat.

## Aplicativos embutidos

Você pode enviar aplicativos para um chat - jogos, editores, enquetes e outras ferramentas. Isso torna o Delta Chat um mensageiro realmente extensível.

### Onde posso obter aplicativos embutidos?

- In a chat, using Attachment Button → Apps

- You can also create your own app and attach it using Attachment Button → File

### How private are in-chat apps?

- In-chat apps can not send data to the Internet, or download anything.

- An in-chat app can only exchange data within a chat, with its copies on the devices of your chat partners. Other than that, it’s completely isolated from the Internet.

- The privacy an in-chat app offers is the privacy of your chat - as long as you trust the people you chat with, you can trust the in-chat app as well.

- This also means: Just like for web links, do not open apps from untrusted contacts.

### How can I create my own in-chat apps?

- In-chat apps are zip files with `.xdc` extension containing html, css, and javascript code.

- You can extend the Hello World example app to get started.

- All else you need to know is written in the Webxdc documentation.

- If you have question, you can ask others with experience in the Delta Chat Forum.

## Instant message delivery and Push Notifications

### What are Push Notifications? How can I get instant message delivery?

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.

Push Notifications work with all chatmail servers on

- iOS devices, by integrating with Apple Push services.

- Android devices, by integrating with the Google FCM Push service, including on devices that use microG instead of proprietary Google code on the phone.

### Are Push Notifications enabled on iOS devices? Is there an alternative?

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.

### Are Push notifications enabled / needed on Android devices?

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:

- Use Background Connection: If you are not using a Push service, you may disable “battery optimizations” for Delta Chat, allowing it to fetch messages in the background. However, there could be delays from minutes to hours. Some Android vendors even restrict apps completely (see dontkillmyapp.com) and Delta Chat might not show incoming messages until you manually open the app again.

- Force Background Connection: This is the fallback option if the previous options are not available or do not achieve “instant delivery”. Enabling it causes a permanent notification on your phone which may sometimes be “minified” with recent Android phones.

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

### How private are Delta Chat Push Notifications?

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.

Here is how Delta Chat apps perform Push Notification delivery:

- A Delta Chat app obtains a “device token” locally, encrypts it and stores it on the chatmail server.

- When a chatmail server receives a message for a Delta Chat user it forwards the encrypted device token to the central Delta Chat notification proxy.

- The central Delta Chat notification proxy decrypts the device token and forwards it to the respective Push service (Apple, Google, etc.), without ever knowing the IP or profile data of Delta Chat users.

- The central Push Service (Apple, Google, etc.) wakes up the Delta Chat app on your device to check for new messages in the background. It does not know about the profile data of the device it wakes up. The central Apple/Google Push services never see any profile data (sender or receiver) and also never see any message content (also not in encrypted forms).

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 :)

## Multi-cliente

### Posso usar o Delta Chat em vários dispositivos ao mesmo tempo?

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

- Make sure both devices are on the same Wi-Fi or network

- On the first device, go to Settings → Add Second Device, unlock the screen if needed and wait a moment until a QR code is shown

- On the second device, install Delta Chat

- On the second device, start Delta Chat, select Add as Second Device, and scan the QR code from the old device

- Transfer should start after a few seconds and during transfer both devices will show the progress. Wait until it is finished on both devices.

In contrast to many other messengers, after successful transfer, both devices are completely independent. One device is not needed for the other to work.

### Troubleshooting

- Double-check both devices are in the same Wi-Fi or network

- On Windows, go to “Control Panel / Network and Internet” and make sure, Private Network is selected as “Network profile type” (after transfer, you can change back to the original value)

- On iOS, make sure “System Settings / Apps / Delta Chat / Local Network” access is granted

- On macOS, enable “System Settings / Privacy & Security / Local Network / Delta Chat”

- Your system might have a “personal firewall”, which is known to cause problems (especially on Windows). Disable the personal firewall for Delta Chat on both ends and try again

- Guest Networks may not allow devices to communicate with each other. If possible, use a non-guest network.

- If you still have troubles using the same network, try to open Mobile Hotspot on one device and join that Wi-Fi from the other one

- Ensure there is enough storage on the destination device

- If transfer started, make sure, the devices stay active and do not fall asleep. Do not exit Delta Chat. (we try hard to make the app work in background, but systems tend to kill apps, unfortunately)

- Delta Chat is already logged in on the destination device? You can use multiple profiles per device, just add another profile

- If you still have problems or if you cannot scan a QR code try the manual transfer described below

### Manual Transfer

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

- On the old device, go to Settings → Chats → Export 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, select I Already Have a Profile → Restore from Backup. If you use iOS and encounter difficulties, this guide might help you.

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

### Existe algum plano para a introdução de um cliente Web para Delta Chat?

- Não há planos imediatos, mas algumas reflexões preliminares.
- Há 2-3 vias para a introdução de um cliente Delta Chat Web, mas todas são trabalho significativo. Por enquanto, nos concentramos em obter lançamentos estáveis em todos os app stores (Google Play/iOS/Windows/macOS/Linux repositórios) como aplicativos nativos.
- Se você precisa de um Cliente Web, porque não está autorizado a instalar software em o computador com o qual você trabalha, você pode usar o Windows Desktop Client portátil, ou o AppImage para Linux. Você pode encontrá-los em get.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 are Relays?

Relays are used to temporarily hold messages in case your device is offline. Relays are cheap and dumb servers, that do not store data as group states, your name or avatar - all that exist only on your device. Relays are operated by different groups and people.

By default, after installation, a relay is automatically set up, so you do not need to care about that. However, if you want to, you can configure relays at Settings → Advanced → Relays:

- You can add a relay by scanning its QR code; chatmail.at/relays shows some known ones. If you have multiple relays, you will receive messages on all of them. Contacts learn your current relays automatically when you message them.

- Tap on a relay to set it as used for sending.

- If you remove a relay, contacts who only know this relay may not reach you until you message them again. To stay reachable in the meantime, choose Hide from Contacts in the confirmation dialog instead of removing it right away.

- To show a hidden relay again, tap on it.

For more details and future possibilities of relays, you can follow discussions in the Forum.

### 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:

- Non-chatmail apps are largely not accomplishing automatic end-to-end email encryption for their users, while chatmail apps and relays pervasively enforce end-to-end encryption and security standards.

- Non-chatmail apps use email servers as a long-term message archive while chatmail clients use email servers for ephemeral instant message relay.

- Supporting the full variety of classic email setups would require considerable development and maintenance efforts, and complicate making chatmail-based messaging more resilient, reliable and fast.

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

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 Relay. 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 .

### 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.

### 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:

- How many contacts are introduced by personally scanning a QR code?

- Which versions of Delta Chat are being used?

- What errors occur for users?

We will not collect any personally identifiable information about you.

### Estou interessado nos detalhes técnicos. Pode me dizer mais?

Veja As normas usadas no Delta Chat.

## Encryption and Security

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

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

- Secure-Join to exchange encryption setup information through QR-code scanning or “invite links”.

- Autocrypt is used for automatically establishing end-to-end encryption between contacts and all members of a group chat.

- Autocrypt v2, scheduled for full implementation in 2026, will bring post-quantum resistant encryption and forward secrecy.

- Sharing a contact to a chat enables receivers to use end-to-end encryption with the contact.

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 .

### What does the green checkmark in a contact profile mean?

A contact profile might show a 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.

For more in-depth discussion of “guaranteed end-to-end encryption” please see Secure-Join protocols and specifically read about “Verified Groups”, the technical term of what is called here “green-checkmarked” or “guaranteed end-to-end encrypted” chats.

### Are attachments (pictures, files, audio etc.) end-to-end encrypted?

Sim.

When we talk about an “end-to-end encrypted message” we always mean a whole message is encrypted, including all the attachments and attachment metadata such as filenames.

### Is OpenPGP secure?

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.

### Is Delta Chat vulnerable to 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.

### How does Delta Chat protect metadata in messages?

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:

- Sender and receiver addresses, randomly generated by default
- Message size

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

### How to protect metadata and contacts when a device is seized?

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.

### Who sees my IP Address?

The used relays need to know your IP Address, as well as sometimes your contact’s devices if you have a call or use apps together.

IP Addresses are needed for connectivity and efficiency. Delta Chat neither persists nor exposes them. Note that IP Addresses are not like an address you give to a delivery service, but typically less precise, often defining city or region only.

If you see your IP Address as a risk, we recommend to use a VPN for the whole system. Per-app options leave gaps across your system. For example, tapping a link can expose IP Addresses to unknown parties, which is by far the larger risk.

### 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.

### Does Delta Chat support Perfect Forward Secrecy?

Not yet, but it’s coming with Autocrypt v2.

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.

Autocrypt v2, scheduled for full implementation in 2026, will provide reliable deletion (forward secrecy) through automatic key rotation. This approach is specified in the Autocrypt v2 OpenPGP Certificates draft.

### Does Delta Chat support Post-Quantum-Cryptography?

Not yet, but it’s coming with Autocrypt v2.

Autocrypt v2, scheduled for full implementation in 2026, will bring post-quantum resistant encryption to protect against quantum computer attacks. Delta Chat uses the Rust OpenPGP library rPGP which supports the latest IETF Post-Quantum-Cryptography OpenPGP draft. The implementation is specified in the Autocrypt v2 OpenPGP Certificates draft.

### How can I manually check encryption information?

You may check the end-to-end encryption status manually in the “Encryption” dialog (user profile on Android/iOS or right-click a user’s chat-list item on desktop). Delta Chat shows two fingerprints there. If the same fingerprints appear on your own and your contact’s device, the connection is safe.

### Posso reutilizar minha chave 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.

### Was Delta Chat independently audited for security vulnerabilities?

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

- 2024 December, an NLNET-commissioned Evaluation of rPGP by Radically Open Security took place. rPGP serves as the end-to-end encryption OpenPGP engine of Delta Chat. Two advisories were released related to the findings of this audit:

  - “Panics on Malformed Untrusted Input” CVE-2024-53856
  - “Potential Resource Exhaustion when handling Untrusted Messages” CVE-2024-53857

  The issues outlined in these advisories have been fixed and are part of Delta Chat releases on all appstores since December 2024.

- 2024 March, we received a deep security analysis from the Applied Cryptography research group at ETH Zuerich and addressed all raised issues. See our blog post about Hardening Guaranteed End-to-End encryption for more detailed information and the Cryptographic Analysis of Delta Chat research paper published afterwards.

- 2023 April, we fixed security and privacy issues with the “web apps shared in a chat” feature, related to failures of sandboxing especially with Chromium. We subsequently got an independent security audit from Cure53 and all issues found were fixed in the 1.36 app series released in April 2023. See here for the full background story on end-to-end security in the web.

- 2023 March, Cure53 analyzed both the transport encryption of Delta Chat’s network connections and a reproducible mail server setup as recommended on this site. You can read more about the audit on our blog or read the full report here.

- 2020, Include Security analyzed Delta Chat’s Rust core, IMAP, SMTP, and TLS libraries. It did not find any critical or high-severity issues. The report raised a few medium-severity weaknesses - they are no threat to Delta Chat users on their own because they depend on the environment in which Delta Chat is used. For usability and compatibility reasons, we can not mitigate all of them and decided to provide security recommendations to threatened users. You can read the full report here.

- 2019, Include Security analyzed Delta Chat’s PGP and RSA libraries. It found no critical issues, but two high-severity issues that we subsequently fixed. It also revealed one medium-severity and some less severe issues, but there was no way to exploit these vulnerabilities in the Delta Chat implementation. Some of them we nevertheless fixed since the audit was concluded. You can read the full report here.

## Diverso

### Quais permissões o Delta Chat precisa?

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:

- The official website, https://delta.chat/download shows all options in detail

- If unavailable, use the mirror at https://deltachat.github.io/deltachat-pages

- Open one of the following app stores and search for “Delta Chat”: Google Play Store, F-Droid, Huawei App Gallery, iOS and macOS App Store, Microsoft Store

- Check the package manager of your Linux distributions

- Android APKs are also available on https://github.com/deltachat/deltachat-android/releases

### Como são os desenvolvimentos do Delta Chat financiados?

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:

- In 2023 and 2024 we got accepted in the Next Generation Internet (NGI) program for our work in webxdc PUSH, along with collaboration partners working on webxdc evolve, webxdc XMPP, DeltaTouch and DeltaTauri. All of these projects are partially completed or to be completed in early 2025.

- In 2021 we received further EU funding for two Next-Generation-Internet proposals, namely for EPPD - email provider portability directory (~97K EUR) and AEAP - email address porting (~90K EUR) which resulted in better multi-profile support, improved QR-code contact and group setups and many networking improvements on all platforms.

- The NLnet foundation granted in 2019/2020 EUR 46K for completing Rust/Python bindings and instigating a Chat-bot eco-system.

- The Open Technology Fund gave us a first 2018/2019 grant (~$200K) during which we majorly improved the Android app and released a first Desktop app beta version, and which moreover moored our feature developments in UX research in human rights contexts, see our concluding Needfinding and UX report. The second 2019/2020 grant (~$300K) helped us to release Delta/iOS versions, to convert our core library to Rust, and to provide new features for all platforms.

- The NEXTLEAP EU project funded the research and implementation of verified groups and setup contact protocols in 2017 and 2018 and also helped to integrate end-to-end Encryption through Autocrypt.

- Sometimes we receive one-time donations from private individuals. For example, in 2021 a generous individual bank-wired us 4K EUR with the subject “keep up the good developments!”. 💜 We use such money to fund development gatherings or to care for ad-hoc expenses that can not easily be predicted for, or reimbursed from, public funding grants. Receiving more donations also helps us to become more independent and long-term viable as a contributor community.

- Por último, mas não menos importante, vários especialistas pró-bono e entusiastas contribuíram e contribuir aos desenvolvimentos do Delta Chat sem receber dinheiro, ou apenas pequenas quantidades. Sem elas, o Delta Chat não estaria onde está hoje, não mesmo perto.

The monetary funding mentioned above is mostly organized by merlinux GmbH in Freiburg (Germany), and is distributed to more than a dozen contributors world-wide.

Please see Delta Chat Contribution channels for both monetary and other contribution possibilities.