<arel="me"href="https://mastodon.social/@simplex"></a>
- 📱 Mobile apps for Android ([Google Play](https://play.google.com/store/apps/details?id=chat.simplex.app), [APK](https://github.com/simplex-chat/simplex-chat/releases/latest/download/simplex.apk)) and [iOS](https://apps.apple.com/us/app/simplex-chat/id1605771084).
You can connect to the team via the app using "chat with the developers button" available when you have no conversations in the profile, "Send questions and ideas" in the app settings or via our [SimpleX address](https://simplex.chat/contact#/?v=1&smp=smp%3A%2F%2FPQUV2eL0t7OStZOoAsPEV2QYWt4-xilbakvGUGOItUo%3D%40smp6.simplex.im%2FK1rslx-m5bpXVIdMZg9NLUZ_8JBm8xTt%23%2F%3Fv%3D1%26dh%3DMCowBQYDK2VuAyEALDeVe-sG8mRY22LsXlPgiwTNs9dbiLrNuA7f3ZMAJ2w%253D%26srv%3Dbylepyau3ty4czmn77q4fglvperknl4bi2eb2fdy2bh4jxtf32kf73yd.onion). Please connect to:
You can join the groups created by other users via the new [directory service](https://simplex.chat/contact#/?v=1-4&smp=smp%3A%2F%2Fu2dS9sG8nMNURyZwqASV4yROM28Er0luVTx5X1CsMrU%3D%40smp4.simplex.im%2FeXSPwqTkKyDO3px4fLf1wx3MvPdjdLW3%23%2F%3Fv%3D1-2%26dh%3DMCowBQYDK2VuAyEAaiv6MkMH44L2TcYrt_CsX3ZvM11WgbMEUn0hkIKTOho%253D%26srv%3Do5vmywmrnaxalvz6wi3zicyftgio6psuvyniis6gco6bp6ekl4cqj4id.onion). We are not responsible for the content shared in these groups.
- having preliminary approved with the admin in direct message, share the link to a group you created, but only once. Once the group has more than 10 members it can be submitted to [SimpleX Directory Service](./docs/DIRECTORY.md) where the new users will be able to discover it.
- avoid spam (too frequent messages, even if they are relevant)
- avoid any personal attacks or hostility.
- avoid sharing any content that is not relevant to the above (that includes, but is not limited to, discussing politics or any aspects of society other than privacy, security, technology and communications, sharing any content that may be found offensive by other users, etc.).
Messages not following these rules will be deleted, the right to send messages may be revoked, and the access to the new members to the group may be temporarily restricted, to prevent re-joining under a different name - our imperfect group moderation does not have a better solution at the moment.
You can join an English-speaking users group if you want to ask any questions: [#SimpleX users group](https://simplex.chat/contact#/?v=2-4&smp=smp%3A%2F%2FPQUV2eL0t7OStZOoAsPEV2QYWt4-xilbakvGUGOItUo%3D%40smp6.simplex.im%2Fos8FftfoV8zjb2T89fUEjJtF7y64p5av%23%2F%3Fv%3D1-2%26dh%3DMCowBQYDK2VuAyEAQqMgh0fw2lPhjn3PDIEfAKA_E0-gf8Hr8zzhYnDivRs%253D%26srv%3Dbylepyau3ty4czmn77q4fglvperknl4bi2eb2fdy2bh4jxtf32kf73yd.onion&data=%7B%22type%22%3A%22group%22%2C%22groupLinkId%22%3A%22lBPiveK2mjfUH43SN77R0w%3D%3D%22%7D)
There is also a group [#simplex-devs](https://simplex.chat/contact#/?v=1-4&smp=smp%3A%2F%2FPQUV2eL0t7OStZOoAsPEV2QYWt4-xilbakvGUGOItUo%3D%40smp6.simplex.im%2FvYCRjIflKNMGYlfTkuHe4B40qSlQ0439%23%2F%3Fv%3D1-2%26dh%3DMCowBQYDK2VuAyEAHNdcqNbzXZhyMoSBjT2R0-Eb1EPaLyUg3KZjn-kmM1w%253D%26srv%3Dbylepyau3ty4czmn77q4fglvperknl4bi2eb2fdy2bh4jxtf32kf73yd.onion&data=%7B%22type%22%3A%22group%22%2C%22groupLinkId%22%3A%22PD20tcXjw7IpkkMCfR6HLA%3D%3D%22%7D) for developers who build on SimpleX platform:
There are groups in other languages, that we have the apps interface translated into. These groups are for testing, and asking questions to other SimpleX Chat users:
You need to share a link with your friend or scan a QR code from their phone, in person or during a video call, to make a connection and start messaging.
The channel through which you share the link does not have to be secure - it is enough that you can confirm who sent you the message and that your SimpleX connection is established.
<imgsrc="https://github.com/simplex-chat/.github/blob/master/profile/images/app1.png"alt="Make a private connection"height="360"><imgsrc="https://github.com/simplex-chat/.github/blob/master/profile/images/arrow.png"height="360"><imgsrc="https://github.com/simplex-chat/.github/blob/master/profile/images/app2.png"alt="Conversation"height="360"><imgsrc="https://github.com/simplex-chat/.github/blob/master/profile/images/arrow.png"height="360"><imgsrc="https://github.com/simplex-chat/.github/blob/master/profile/images/app3.png"alt="Video call"height="360">
After you connect, you can [verify connection security code](./blog/20230103-simplex-chat-v4.4-disappearing-messages.md#connection-security-verification).
Thanks to our users and [Weblate](https://hosted.weblate.org/engage/simplex-chat/), SimpleX Chat apps, website and documents are translated to many other languages.
Join our translators to help SimpleX grow!
|locale|language |contributor|[Android](https://play.google.com/store/apps/details?id=chat.simplex.app) and [iOS](https://apps.apple.com/us/app/simplex-chat/id1605771084)|[website](https://simplex.chat)|Github docs|
Languages in progress: Arabic, Japanese, Korean, Portuguese and [others](https://hosted.weblate.org/projects/simplex-chat/#languages). We will be adding more languages as some of the already added are completed – please suggest new languages, review the [translation guide](./docs/TRANSLATIONS.md) and get in touch with us!
Huge thank you to everybody who donated to SimpleX Chat!
We are prioritizing users privacy and security - it would be impossible without your support.
Our pledge to our users is that SimpleX protocols are and will remain open, and in public domain, - so anybody can build the future implementations of the clients and the servers. We are building SimpleX platform based on the same principles as email and web, but much more private and secure.
Everyone should care about privacy and security of their communications - innocuous conversations can put you in danger even if there is nothing to hide.
One of the most shocking stories is the experience of [Mohamedou Ould Salahi](https://en.wikipedia.org/wiki/Mohamedou_Ould_Slahi) that he wrote about in his memoir and that is shown in The Mauritanian movie. He was put into Guantanamo camp, without trial, and was tortured there for 15 years after a phone call to his relative in Afghanistan, under suspicion of being involved in 9/11 attacks, even though he lived in Germany for the 10 years prior to the attacks.
It is not enough to use an end-to-end encrypted messenger, we all should use the messengers that protect the privacy of our personal networks - who we are connected with.
**Unlike any other existing messaging platform, SimpleX has no identifiers assigned to the users** - not even random numbers. This protects the privacy of who are you communicating with, hiding it from SimpleX platform servers and from any observers. [Read more](./docs/SIMPLEX.md#full-privacy-of-your-identity-profile-contacts-and-metadata).
As you have no identifier on SimpleX platform, you cannot be contacted unless you share a one-time invitation link or an optional temporary user address. [Read more](./docs/SIMPLEX.md#the-best-protection-against-spam-and-abuse).
SimpleX stores all user data on client devices, the messages are only held temporarily on SimpleX relay servers until they are received. [Read more](./docs/SIMPLEX.md#complete-ownership-control-and-security-of-your-data).
You can use SimpleX with your own servers and still communicate with people using the servers that are pre-configured in the apps or any other SimpleX servers. [Read more](./docs/SIMPLEX.md#users-own-simplex-network).
1._How SimpleX can deliver messages without any user identifiers?_ See [v2 release announcement](./blog/20220511-simplex-chat-v2-images-files.md#the-first-messaging-platform-without-user-identifiers) explaining how SimpleX works.
2._Why should I not just use Signal?_ Signal is a centralized platform that uses phone numbers to identify its users and their contacts. It means that while the content of your messages on Signal is protected with robust end-to-end encryption, there is a large amount of meta-data visible to Signal - who you talk with and when.
3._How is it different from Matrix, Session, Ricochet, Cwtch, etc., that also don't require user identities?_ Although these platforms do not require a _real identity_, they do rely on anonymous user identities to deliver messages – it can be, for example, an identity key or a random number. Using a persistent user identity, even anonymous, creates a risk that user's connection graph becomes known to the observers and/or service providers, and it can lead to de-anonymizing some users. If the same user profile is used to connect to two different people via any messenger other than SimpleX, these two people can confirm if they are connected to the same person - they would use the same user identifier in the messages. With SimpleX there is no meta-data in common between your conversations with different contacts - the quality that no other messaging platform has.
[Mar 8, 2025. SimpleX Chat v6.3: new user experience and safety in public groups](./blog/20250308-simplex-chat-v6-3-new-user-experience-safety-in-public-groups.md)
[Jan 14, 2025. SimpleX network: large groups and privacy-preserving content moderation](./blog/20250114-simplex-network-large-groups-privacy-preserving-content-moderation.md)
[Dec 10, 2024. SimpleX network: preset servers operated by Flux, business chats and more with v6.2 of the apps](./20241210-simplex-network-v6-2-servers-by-flux-business-chats.md)
[Oct 14, 2024. SimpleX network: security review of protocols design by Trail of Bits, v6.1 released with better calls and user experience.](./blog/20241014-simplex-network-v6-1-security-review-better-calls-user-experience.md)
[Aug 14, 2024. SimpleX network: the investment from Jack Dorsey and Asymmetric, v6.0 released with the new user experience and private message routing](./blog/20240814-simplex-chat-vision-funding-v6-private-routing-new-user-experience.md)
[Jun 4, 2024. SimpleX network: private message routing, v5.8 released with IP address protection and chat themes](./blog/20240604-simplex-chat-v5.8-private-message-routing-chat-themes.md)
[Nov 25, 2023. SimpleX Chat v5.4 released: link mobile and desktop apps via quantum resistant protocol, and much better groups](./blog/20231125-simplex-chat-v5-4-link-mobile-desktop-quantum-resistant-better-groups.md).
[Apr 22, 2023. SimpleX Chat: vision and funding, v5.0 released with videos and files up to 1gb](./blog/20230422-simplex-chat-vision-funding-v5-videos-files-passcode.md).
[Mar 1, 2023. SimpleX File Transfer Protocol – send large files efficiently, privately and securely, soon to be integrated into SimpleX Chat apps.](./blog/20230301-simplex-file-transfer-protocol.md).
[Nov 8, 2022. Security audit by Trail of Bits, the new website and v4.2 released](./blog/20221108-simplex-chat-v4.2-security-audit-new-website.md).
SimpleX is a client-server network with a unique network topology that uses redundant, disposable message relay nodes to asynchronously pass messages via unidirectional (simplex) message queues, providing recipient and sender anonymity.
Unlike P2P networks, all messages are passed through one or several server nodes, that do not even need to have persistence. In fact, the current [SMP server implementation](https://github.com/simplex-chat/simplexmq#smp-server) uses in-memory message storage, persisting only the queue records. SimpleX provides better metadata protection than P2P designs, as no global participant identifiers are used to deliver messages, and avoids [the problems of P2P networks](./docs/SIMPLEX.md#comparison-with-p2p-messaging-protocols).
Unlike federated networks, the server nodes **do not have records of the users**, **do not communicate with each other** and **do not store messages** after they are delivered to the recipients. There is no way to discover the full list of servers participating in SimpleX network. This design avoids the problem of metadata visibility that all federated networks have and better protects from the network-wide attacks.
See [SimpleX whitepaper](https://github.com/simplex-chat/simplexmq/blob/stable/protocol/overview-tjr.md) for more information on platform objectives and technical design.
See [SimpleX Chat Protocol](./docs/protocol/simplex-chat.md) for the format of messages sent between chat clients over [SimpleX Messaging Protocol](https://github.com/simplex-chat/simplexmq/blob/stable/protocol/simplex-messaging.md).
SimpleX Chat is a work in progress – we are releasing improvements as they are ready. You have to decide if the current state is good enough for your usage scenario.
We compiled a [glossary of terms](./docs/GLOSSARY.md) used to describe communication systems to help understand some terms below and to help compare advantages and disadvantages of various communication systems.
1. Instead of user profile identifiers used by all other platforms, even the most private ones, SimpleX uses [pairwise per-queue identifiers](./docs/GLOSSARY.md#pairwise-pseudonymous-identifier) (2 addresses for each unidirectional message queue, with an optional 3rd address for push notifications on iOS, 2 queues in each connection between the users). It makes observing the network graph on the application level more difficult, as for `n` users there can be up to `n * (n-1)` message queues.
2. [End-to-end encryption](./docs/GLOSSARY.md#end-to-end-encryption) in each message queue using [NaCl cryptobox](https://nacl.cr.yp.to/box.html). This is added to allow redundancy in the future (passing each message via several servers), to avoid having the same ciphertext in different queues (that would only be visible to the attacker if TLS is compromised). The encryption keys used for this encryption are not rotated, instead we are planning to rotate the queues. Curve25519 keys are used for key negotiation.
3. [Double ratchet](./docs/GLOSSARY.md#double-ratchet-algorithm) end-to-end encryption in each conversation between two users (or group members). This is the same algorithm that is used in Signal and many other messaging apps; it provides OTR messaging with [forward secrecy](./docs/GLOSSARY.md#forward-secrecy) (each message is encrypted by its own ephemeral key) and [break-in recovery](./docs/GLOSSARY.md#post-compromise-security) (the keys are frequently re-negotiated as part of the message exchange). Two pairs of Curve448 keys are used for the initial [key agreement](./docs/GLOSSARY.md#key-agreement-protocol), initiating party passes these keys via the connection link, accepting side - in the header of the confirmation message.
4. [Post-quantum resistant key exchange](./docs/GLOSSARY.md#post-quantum-cryptography) in double ratchet protocol *on every ratchet step*. Read more in [this post](./blog/20240314-simplex-chat-v5-6-quantum-resistance-signal-double-ratchet-algorithm.md) and also see this [publication by Apple]( https://security.apple.com/blog/imessage-pq3/) explaining the need for post-quantum key rotation.
5. Additional layer of encryption using NaCL cryptobox for the messages delivered from the server to the recipient. This layer avoids having any ciphertext in common between sent and received traffic of the server inside TLS (and there are no identifiers in common as well).
6. Several levels of [content padding](./docs/GLOSSARY.md#message-padding) to frustrate message size attacks.
7. All message metadata, including the time when the message was received by the server (rounded to a second) is sent to the recipients inside an encrypted envelope, so even if TLS is compromised it cannot be observed.
8. Only TLS 1.2/1.3 are allowed for client-server connections, limited to cryptographic algorithms: CHACHA20POLY1305_SHA256, Ed25519/Ed448, Curve25519/Curve448.
9. To protect against replay attacks SimpleX servers require [tlsunique channel binding](https://www.rfc-editor.org/rfc/rfc5929.html) as session ID in each client command signed with per-queue ephemeral key.
10. To protect your IP address from unknown messaging relays, and for per-message transport anonymity (compared with Tor/VPN per-connection anonymity), from v6.0 all SimpleX Chat clients use private message routing by default. Read more in [this post](./blog/20240604-simplex-chat-v5.8-private-message-routing-chat-themes.md#private-message-routing).
11. To protect your IP address from unknown file relays, when SOCKS proxy is not enabled SimpleX Chat clients ask for a confirmation before downloading the files from unknown servers.
12. To protect your IP address from known servers all SimpleX Chat clients support accessing messaging servers via Tor - see [v3.1 release announcement](./blog/20220808-simplex-chat-v3.1-chat-groups.md) for more details.
13. Local database encryption with passphrase - your contacts, groups and all sent and received messages are stored encrypted. If you used SimpleX Chat before v4.0 you need to enable the encryption via the app settings.
14. Transport isolation - different TCP connections and Tor circuits are used for traffic of different user profiles, optionally - for different contacts and group member connections.
15. Manual messaging queue rotations to move conversation to another SMP relay.
16. Sending end-to-end encrypted files using [XFTP protocol](https://simplex.chat/blog/20230301-simplex-file-transfer-protocol.html).
1. Automatic message queue rotation and redundancy. Currently the queues created between two users are used until the queue is manually changed by the user or contact is deleted. We are planning to add automatic queue rotation to make these identifiers temporary and rotate based on some schedule TBC (e.g., every X messages, or every X hours/days).
2. Message "mixing" - adding latency to message delivery, to protect against traffic correlation by message time.
- create chat bots and services in any language running SimpleX Chat terminal CLI as a local WebSocket server. See [TypeScript SimpleX Chat client](./packages/simplex-chat-client/) and [JavaScript chat bot example](./packages/simplex-chat-client/typescript/examples/squaring-bot.js).
Please also join [#simplex-devs](https://simplex.chat/contact#/?v=1-2&smp=smp%3A%2F%2Fu2dS9sG8nMNURyZwqASV4yROM28Er0luVTx5X1CsMrU%3D%40smp4.simplex.im%2F6eHqy7uAbZPOcA6qBtrQgQquVlt4Ll91%23%2F%3Fv%3D1-2%26dh%3DMCowBQYDK2VuAyEAqV_pg3FF00L98aCXp4D3bOs4Sxv_UmSd-gb0juVoQVs%253D%26srv%3Do5vmywmrnaxalvz6wi3zicyftgio6psuvyniis6gco6bp6ekl4cqj4id.onion&data=%7B%22type%22%3A%22group%22%2C%22groupLinkId%22%3A%22XonlixcHBIb2ijCehbZoiw%3D%3D%22%7D) group to ask any questions and share your success stories.
- Privacy-preserving identity server for optional DNS-based contact/group addresses to simplify connection and discovery, but not used to deliver messages:
- keep all your contacts and groups even if you lose the domain.
- the server doesn't have information about your contacts and groups.
[SimpleX protocols and security model](https://github.com/simplex-chat/simplexmq/blob/master/protocol/overview-tjr.md) was reviewed, and had many breaking changes and improvements in v1.0.0.
The implementation security assessment of SimpleX cryptography and networking was done in October 2022 by [Trail of Bits](https://www.trailofbits.com/about) – see [the announcement](./blog/20221108-simplex-chat-v4.2-security-audit-new-website.md).
The cryptographic review of SimpleX protocols was done in July 2024 by Trail of Bits – see [the announcement](./blog/20241014-simplex-network-v6-1-security-review-better-calls-user-experience.md).
SimpleX Chat is still a relatively early stage platform (the mobile apps were released in March 2022), so you may discover some bugs and missing features. We would really appreciate if you let us know anything that needs to be fixed or improved.
The default servers configured in the app are provided on the best effort basis. We are currently not guaranteeing any SLAs, although historically our servers had over 99.9% uptime each.
We have never provided or have been requested access to our servers or any information from our servers by any third parties. If we are ever requested to provide such access or information, we will be following due legal process.
We do not log IP addresses of the users and we do not perform any traffic correlation on our servers. If transport level security is critical you must use Tor or some other similar network to access messaging servers. We will be improving the client applications to reduce the opportunities for traffic correlation.
