SYNC Privacy Policy

Version 2026-10-16 · effective 16 October 2026 · earlier version

This policy explains what personal data SYNC processes, what end-to-end encryption protects and what it does not, what stays on your device, who receives data, how long we keep it and what your rights are. It covers the SYNC apps for iPhone and Mac, this website (axiomic.app), the SYNC pages at sync.axiomic.com.cy, and the pages that open from our emails and links (account activation, password reset and invitations). It is the information we give under Articles 13 and 14 of the EU General Data Protection Regulation (GDPR).

1. Who is responsible

The controller of your personal data is AXIOMIC LTD, registered in the Republic of Cyprus under number HE 480260, Charalampou Mouskou & Grigori Afxentiou 20, Athinodorou Business Center, Floor 3, Office 306, 8010 Paphos, Cyprus. For any privacy question or request, write to [email protected].

2. End-to-end encryption: what it protects and what it does not

What is end-to-end encrypted. In an end-to-end encrypted chat, your device encrypts the text of your messages, replies and edits, your reactions, the photos, videos, files (and their names) and voice messages you send, and the link previews in them, before anything leaves the device. Only the devices of the chat’s members hold the keys to open them. SYNC uses the open Matrix encryption protocols (Olm and Megolm). Our servers store and pass on these messages only in encrypted form; we cannot read them, and neither can our hosting and storage providers.

Which chats. One-to-one and group chats are end-to-end encrypted as soon as everyone in them uses a current version of SYNC; the chat’s info page shows whether a chat is. Encryption is not switched off again once it is on. Messages sent before a chat became encrypted stay as they were, readable by our servers.

What our servers can still see, because SYNC needs it to deliver messages, or because it is not part of a message:

• your account: your email address, name, username, bio and profile photos;
• the names, descriptions and photos of groups, and who is in each chat;
• when a message is sent, by whom and in which chat, and which message a reply, an edit or a reaction belongs to (but not what it says);
• who has read what, who is typing, whether you are online and when you were last active; which messages are pinned; that a message was deleted;
• the cards in a chat that show a call, and the calls themselves (below);
• anything in a chat that is not end-to-end encrypted.

Calls. Voice and video calls are encrypted between each device and our call server, which forwards the audio and video to the other participants. They are not yet end-to-end encrypted: the call server handles them in readable form while it forwards them. Calls are never recorded or stored. In an end-to-end encrypted chat, the call screen tells you that the call is not.

Keys and your recovery key. Each of your devices has its own keys, kept in that device’s keychain. We keep the public part of your devices’ keys, so that other people’s devices can encrypt messages for them. So that a new device can read your earlier messages, SYNC keeps an encrypted backup of your message keys on our server. It is locked with a recovery key that is made on your device and never sent to us; you can save it in iCloud Keychain, copy it or print it. Without the recovery key or another signed-in device of yours, nobody — including us — can restore your encrypted history. You can compare security emoji with a contact in person (Verify in person), and SYNC warns you, and pauses sending, when a contact’s keys change.

End-to-end encryption protects messages on their way and on our servers. It does not stop the people you write to from saving, forwarding or showing what you send.

3. What we process on our servers

• Account: your email address; your name, and your username and bio if you set them; your profile photos; your password, if you set one, stored only as a salted Argon2id hash; the public keys of the passkeys you add (their private keys stay in your keychain or password manager); the authenticator secret, encrypted, if your account uses two-step verification; the version of the Terms you accepted and when; your account ID and your SYNC (Matrix) user ID.
• Messages and content: in end-to-end encrypted chats, encrypted data we cannot read, together with the information listed in section 2; in chats that are not end-to-end encrypted, the content itself (text, replies, edits, reactions, photos, videos, files and voice messages); the names, descriptions and photos of groups.
• Encryption keys: the public keys and signatures of your devices, and your encrypted key backup.
• Contacts: who your contacts are and how each was added (QR code or link, Nearby, email invitation, search or a shared chat), and the invitations you send, including the email address of a person you invite. SYNC does not read or upload your address book.
• Activity: whether you are online and when you were last active, when you are typing, and which messages you have read.
• Calls: who called whom, voice or video, and when the call started, was answered and ended; the audio and video pass through our call server in real time and are not stored.
• Device and technical data: the push tokens of your devices (for messages and for calls), device names and session IDs, the version and platform of the app, the IP addresses your devices connect with, and security records such as sign-ins, password changes and account deletion.
• Safety: the reports you send or that concern you (see section 12), our moderators’ decisions and the emails that tell the sender about them, and the list of people you have blocked.
• Emails: the emails we send you (see section 15 for how long).
• Support: what you write to us and our replies.

We do not collect your location, your address book, health, financial or payment data. SYNC contains no analytics, advertising or crash-reporting software.

4. What stays on your device

Your device keeps what it needs to show your chats without asking our servers each time: decrypted messages and a cache of media, a search index of your messages, voice-message transcripts, the assistant’s data if you turn it on, the AI models you download, and your encryption keys. None of this is sent to us. It is protected by your device’s data protection, the keys stay in the device’s keychain for this device only, and SYNC excludes all of it from iCloud and computer backups; the assistant’s memory is also encrypted with its own key. Signing out of SYNC, or deleting your account, removes your data from the device; downloaded models can be deleted in the app. Your recovery key goes to iCloud Keychain only if you choose to save it there.

5. What other people see

• Anyone on SYNC can find you by searching for three or more letters of your name, the start of your username, or your exact email address, and add you as a contact. Search results show your name and username, never your email address; searching for an exact address does tell the searcher that it has a SYNC account. When someone adds you, we tell you by email and by notification.
• Your contacts and the people who share a chat with you see your name, username, bio and profile photo, whether you are online and when you were last active, when you are typing, and which of their messages you have read.
• In a group, every member sees its messages. In an end-to-end encrypted group, people who join later generally cannot read the messages sent before they joined; in a group that is not end-to-end encrypted, they can.

6. Why we use your data, and on what legal basis

• To provide SYNC — your account, sign-in, contacts and search, messages, media, calls, encryption and key backup, notifications and support — because it is necessary to perform our contract with you (GDPR Art. 6(1)(b)).
• To keep SYNC safe — to prevent spam, fraud and abuse, protect accounts, run the automatic filter, handle reports and enforce the Terms of Use — on the basis of our legitimate interest, and our users’ interest, in a safe service (Art. 6(1)(f)).
• To send service emails — sign-in codes, activation, password reset, security notices, the confirmation of an account deletion, and “someone added you” notices — as part of the contract (Art. 6(1)(b)). An invitation to someone who is not on SYNC yet is sent on the basis of the legitimate interest of the person inviting them (Art. 6(1)(f)); it is sent once and expires after 30 days.
• To comply with the law — for example to answer lawful requests from authorities or act on notices of illegal content (Art. 6(1)(c)).

We cannot read end-to-end encrypted messages, and we do not read or analyse any messages for advertising or profiling. A moderator sees the content of a chat that is not end-to-end encrypted only when someone reports it, when we investigate a serious breach of the Terms, or when the law requires it. We make no automated decisions that have legal or similarly significant effects on you.

7. Notifications

We deliver notifications to your iPhone and Mac through the Apple Push Notification service (APNs), which Apple operates.

• Messages: the notification we send through Apple carries no message text and no sender name — only identifiers (your SYNC ID, the chat and the message) and your unread count. Your device then fetches the message from our server, decrypts it and shows it. If you turn off Settings › Notifications and sounds › Show notification text, it shows only “New message”.
• Calls: an incoming call reaches your device as an Apple push that carries the caller’s name and SYNC ID, the call’s ID and whether it is a video call, so that your device can ring and show who is calling. Apple therefore processes the caller’s name.
• Missed calls and new contacts: these notifications name the person, unless Show notification text is off.

8. Transcription, search and the assistant, on your device

• Voice transcription: when you tap Transcribe, your own device turns the voice message into text with a speech model that runs on it. The recording and the text never leave your device, and the text is never added to the chat. You can turn transcription off in Settings › Assistant and privacy › Voice message transcription. A person you send a voice message to can transcribe it on their device in the same way.
• Search: SYNC searches your messages, and what was said in transcribed voice messages, on your device, with a model built into the app or a larger one you can download.
• Assistant (off unless you turn it on, in Settings › Assistant and privacy › Local assistant; iPhone only): it finds follow-ups and tasks in your chats and answers questions about them, with a model that runs on your iPhone. It may work while your iPhone is charging, at night. Its data stays on your iPhone; turning it off erases that data.
• Model downloads: the speech model (about 650 MB), the larger search model (about 330 MB) and the assistant’s model (about 2.7 GB) are downloaded only when you ask for them, directly from Hugging Face (huggingface.co, operated by Hugging Face, Inc., USA). Hugging Face receives your IP address and the request for the file, as any website does, under its own privacy policy; we send it nothing else, and each file is checked against a fixed fingerprint before it is used. You can delete the models in the app.

We do not receive the recordings, transcripts, questions, answers or anything else these features work with, and we do not use any of it to train AI.

9. Link previews

When you send a message with a link, your device fetches the page to make a preview (its title, description and picture) and sends the preview inside the message — encrypted, in an end-to-end encrypted chat. The website sees your device’s IP address, as when you open a page; no cookies are sent. In a chat that is not end-to-end encrypted, our server may fetch the preview for the people who receive it (the website then sees our server’s address), or their device does. On iPhone, links you tap open in Safari’s view inside the app.

10. Without internet (Bluetooth)

Settings › Without internet is off unless you turn it on, and is available on iPhone. When it is on, your iPhone passes text messages of your end-to-end encrypted chats over Bluetooth to and through other iPhones nearby that have SYNC with the same setting on, so that messages can arrive where there is no internet. The messages stay end-to-end encrypted and are sealed again for the trip: the phones that carry them cannot read them or see who sent them; they see only that a SYNC packet passed, when it was made and a tag that changes every day. A carrying phone holds packets in memory only, for at most 6 hours. While the setting is on, SYNC may keep using Bluetooth when it is in the background. Nothing of this reaches us.

11. Adding contacts

• Nearby (iPhone): while Add contact › Nearby is open, iPhones next to each other with SYNC open find each other over the local network and Bluetooth and exchange the names of their owners and a token to measure distance. Holding the phones together, or tapping Add, exchanges an invitation that is valid for 10 minutes. The distance is measured on the phones and is not sent to us.
• QR code or link: your invitation link works for 7 days; whoever opens it and accepts becomes your contact, and you theirs.
• Email invitation: if the person is on SYNC, they become your contact; if not, we email them an invitation once (see section 6).

12. Reports, blocking and the automatic filter

• Reports: when you report a message or a person, we receive the reason you type, the identifier of the message, and who reported whom (by name and SYNC ID). For a message in a chat that is not end-to-end encrypted, our moderators can read the message. For an end-to-end encrypted message they cannot, so please describe the problem in the reason, or send a screenshot to [email protected].
• Blocking: the list of people you block is stored with your account, so that it applies on all your devices.
• Automatic filter: our servers automatically check what they can read against a list of slurs, threats and terms linked to the sexual exploitation of children: the name you sign up with, any new name you take in a chat, the names and descriptions of groups, and the messages, file names and reactions in chats that are not end-to-end encrypted. End-to-end encrypted messages cannot be checked. Something that matches is refused — the message is not sent, or the name is not set — and the refused text is not stored; we keep only a log entry that a refusal happened and which list entry matched. No person reads anything for this check, and it is used for nothing else. We do this on the basis of our legitimate interest, and our users’ interest, in a safe service (Art. 6(1)(f)). If you think something was refused by mistake, write to [email protected].

13. Who receives your data

Your messages and content go to the people you send them to: the members of the chat.

We use these service providers (processors). They process data only on our instructions and under a data processing agreement:

• Contabo GmbH (Germany): hosts, in the European Union, the servers that run our database, message server, call server, push server and this website.
• Cloudflare, Inc. (USA): network and security. Traffic to our app servers and to this website passes through Cloudflare, which terminates the TLS connection as a proxy and so processes your IP address and the requests in transit — for end-to-end encrypted chats, only in encrypted form. Calls do not pass through Cloudflare.
• Cloudflare R2 (Cloudflare, Inc.): stores photos, videos, files and voice messages (encrypted, when they were sent in an end-to-end encrypted chat), and profile and group photos.
• Apple (Apple Push Notification service): delivers notifications and incoming calls to your devices, as described in section 7.
• Resend (USA): sends our emails, including sign-in codes and the emails that tell our moderators about a report; it receives the recipient’s email address and the email’s content.

Some companies receive data from your device directly, under their own terms and privacy policies, only when you use the feature: Hugging Face, when you download a model (section 8); the websites whose links you send or open (section 9); and Apple, if you save your recovery key in iCloud Keychain.

We disclose data to authorities or courts when the law requires it, and when it is needed to protect someone’s safety; we cannot disclose the content of end-to-end encrypted messages, because we cannot read it. We never sell personal data and never share it for advertising. If our business is reorganised or sold, data may pass to the successor, which remains bound by this policy.

14. Transfers outside the European Economic Area

Some of our providers are based in the United States, and Cloudflare (including R2 storage) may process and store data in data centres outside the European Economic Area. Such transfers rely on the European Commission’s adequacy decision for the EU–U.S. Data Privacy Framework, for providers certified under it, or on the European Commission’s Standard Contractual Clauses. You can ask us for a copy of these safeguards at [email protected].

15. How long we keep data

• Messages (encrypted or not, with replies, edits, reactions and call cards): 730 days (two years) after they are sent, then deleted automatically. A message you delete disappears from the chat for everyone at once, and its content is erased from our server within 7 days.
• Photos, videos, files, voice messages and profile photos: until the account that uploaded them is deleted, even if the message that carried them was deleted or has expired. They can only be downloaded by a signed-in SYNC user. Within 30 days of the account’s deletion they are deleted from our servers and from Cloudflare R2 (see section 16).
• Encryption keys and the key backup: while your account exists; a device’s keys go when you remove the device.
• Account data and contacts: while your account exists. Invitation links expire after 7 days (Nearby: 10 minutes) and email invitations after 30 days; the record of an invitation, including the invited address, is kept until the account that sent it is deleted.
• IP addresses and device details of your sessions: up to 28 days on the message server. Other server logs, and the logs of Cloudflare and of this website, are kept for a limited time to run and secure the service.
• Emails we sent: the content of an email is erased from our database 7 days after it was sent; the record that it was sent (recipient and subject) stays while the account exists. A sign-in code expires after 10 minutes. The email confirming an account deletion keeps neither your address nor your name once it has been sent.
• Push tokens: until you sign out, turn notifications off on the device, or delete your account.
• Call records: while your account exists; after a deletion, only records that no longer show your name or email address remain.
• Reports: for as long as we need them to handle the report and any dispute or legal claim that follows. They refer to people by SYNC ID; the emails to our moderators about them, which also give names, are erased 7 days after they are sent, and at once when the account of the reporter or of the sender is deleted.
• Security audit log: records of security-relevant actions (such as sign-up, sign-in, account deletion and moderation decisions), with technical details of the request, are kept as a lasting security record. They never contain the content of messages.
• On your device: until you delete it in the app, sign out or remove the app (section 4).

16. Deleting your account

You can delete your account in the app: Settings › Account › Delete account, confirmed with your password or with a code we email you. Then:

• at once: you can no longer sign in, you are signed out on every device and all your sessions end, your contacts, invitations and notification registrations are removed, chats show you as “Deleted account” without your photo, and your email address, name and profile are removed from your account record, so the address can be used again;
• in the background, normally within minutes and at the latest within 30 days: the messages you sent are removed from every chat, the photos, videos, files and voice messages you uploaded are deleted from our servers and from Cloudflare R2, and your SYNC (Matrix) account and its devices are closed and erased;
• we send a confirmation to your email address; once it has been sent, we keep only the record that it was sent, without your address or name.

What remains: the security audit log (without message content); call records and reports that refer to the deleted account without your name or email address; reactions you added in chats that were not end-to-end encrypted, shown as “Deleted account”; and copies that other people made themselves, such as screenshots or forwarded messages.

If you can no longer sign in, write to [email protected] from the account’s email address and we will delete the account for you.

17. How we protect your data

Besides end-to-end encryption, every connection to our servers uses TLS (HTTPS). Passwords are stored only as salted hashes, sign-in codes expire after 10 minutes, and repeated wrong attempts lock sign-in for a while. Our servers are isolated from each other, so that each can be reached only by the services that need it, and our staff tools require two-step verification. No system is perfectly secure; if a breach affects your personal data, we will tell you and the supervisory authority as the law requires.

18. Your rights

Under the GDPR you have the right to access your personal data and get a copy of it; to have it corrected (you can change your name, username, bio and photos in the app); to have it erased (you can delete your account in the app); to restrict its processing; to receive the data you gave us in a portable format; to object to processing based on legitimate interests; and to withdraw a consent at any time, without affecting what was done before. We cannot provide the content of end-to-end encrypted messages, because we cannot read it; it is on your devices.

To use these rights, write to [email protected], if possible from your account’s email address. We answer within one month and may ask you to confirm your identity.

You may also complain to a supervisory authority: in Cyprus, the Commissioner for Personal Data Protection, 1 Iasonos Street, 1082 Nicosia (P.O. Box 23378, 1682 Nicosia), phone +357 22 818 456, email [email protected], www.dataprotection.gov.cy; or the authority of the EU country where you live or work.

19. Children

SYNC is only for people aged 16 or older; everyone confirms their age when they sign up. We do not knowingly collect data from anyone younger; when we learn that an account belongs to someone under 16, we close it and delete its data. If you think a child is using SYNC, tell us at [email protected].

20. Permissions on your device

SYNC asks for access only when you use a feature that needs it: the camera (photos, videos, video calls and scanning QR codes), the microphone (voice messages and calls), your photos (to send or save them), the local network and Nearby Interaction (only while Add contact › Nearby is open), Bluetooth (only for Without internet and Nearby), and notifications. Face ID or Touch ID is used only by your device to confirm a passkey; SYNC never receives biometric data. You can change these permissions in your device’s Settings at any time.

21. This website and the Mac downloads

axiomic.app sets no cookies and runs no scripts, analytics or advertising. Cloudflare, which delivers it, and our web server process your IP address and the details your browser sends in order to deliver and protect the pages; Cloudflare may set strictly necessary security cookies.

SYNC for Mac is downloaded from sync.axiomic.com.cy, and checks there for updates about every six hours. Each check tells our server the app’s name and version, and the server sees your IP address; updates are installed only when you agree.

22. Changes to this policy

We update this policy when SYNC, our providers or the law change. The version and date at the top show the current version; earlier versions stay available from the link there. We tell you in the app about important changes.

23. Contact

AXIOMIC LTD (HE 480260), Charalampou Mouskou & Grigori Afxentiou 20, Athinodorou Business Center, Floor 3, Office 306, 8010 Paphos, Cyprus.
Email: [email protected]