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There are no phone numbers or usernames to search, so you swap contact cards:

• In person: Contacts → Add contact → Scan their code, and point the camera at the QR code on their My card screen. Or tap Show my code and let them scan yours.
• Remotely: open My card → Share link and send the link however you like. When they open it, Nullchat offers to send you a request. You can also paste a contact link or an npub1… key into Contacts → Add contact.

The other person sees you under Contacts → Requests and taps Accept. Until then you appear under “Waiting for them to accept”.

Names and avatars can be copied by anyone. To be sure, open Chat info → Verify safety code and compare the 12-digit code with the other person in person or on a call. If they match, tap Mark as verified. Nullchat warns you if a verified contact’s key ever changes, or if someone else uses their name.

Anyone who knows your public key can send you a request, but it lands in Contacts → Requests, not in your chats, and notifications for it never show the content. Accept, ignore or block it. Other Nostr apps can also send you plain-text NIP-17 messages; they show up as requests too.

Contacts → New group, pick up to 31 contacts, and name it. Each member gets their own encrypted copy of every message, so there’s no group server. The creator is the admin and can add or remove members.

A chat where every message self-destructs a few seconds after it’s read. Tap the ghost icon at the top of a chat, choose Vanish 5, 10 or 30 seconds after reading, then Turn on and clear.

• Turning dark mode on or off clears the conversation on both phones, so old messages can’t leak into the dark chat and dark messages can’t stay behind.
• When a message is shown on the reader’s screen, a countdown ring starts. At zero it’s deleted on both phones.
• Read receipts are always on in dark chats, since they start the timer.
• Screenshots and screen recording are blocked while the chat is open. On iPhone a screenshot can only be detected afterwards, so the other person sees “Screenshot taken” instead.
• Dark chats stay on your phone. Linked browsers and Macs show “Dark chat, open on your phone”.

From every honest Nullchat app, yes. But disappearing messages are a courtesy, not magic: someone can photograph their screen with another camera, or use a modified app that ignores the timer. Only send what you’d be comfortable with the other person keeping. An unread dark message is kept for at most 7 days.

In a chat, tap the attach button, pick or take a photo, turn on View once on the preview, and send. The recipient can open it once, full screen. It closes after they leave it or after 30 seconds, and then it’s deleted on both phones and the bubble says “Opened”. Screenshots are blocked or reported. View-once photos never appear in notifications, chat previews or on linked devices, and if they aren’t opened within 7 days they expire.

Photos travel inside the encrypted message itself, with no media server, so they are resized to fit within about 80 KB. This also removes location and other metadata from the file.

Twelve words shown when you create your key, and any time later under Settings → Backup phrase. They are your identity. Write them down on paper and keep them somewhere safe. Never type them into a website, and never share them: anyone with the words can read new messages sent to you and send messages as you. We will never ask for them.

On the new phone choose Restore from backup phrase during setup (or Settings → Restore from phrase, which replaces the identity on that phone) and type your 12 words. You keep the same identity, so contacts can keep writing to you, and messages still waiting on relays (up to 7 days old) are fetched. Your chat history and contact list are stored only on the old phone, so they don’t come across. Contacts reappear as they message you, or you can add them again.

Then the identity can’t be recovered, by you or by us. There is no account or server copy. Create a new key and share your new contact card with people. If someone might have your unlocked phone, tell your contacts so they stop trusting the old key.

Without push, Nullchat checks for messages when the system lets it run in the background. On iPhone that can be hours. For quick notifications, turn on Settings → Notifications and make sure the Push wake service field holds a URL (it’s filled in for you). Also allow notifications for Nullchat in the system settings.

Only that some device should be woken. A push says just “New message”. The service never receives the sender, the chat or the content. Your app then fetches and decrypts the message itself. You can run your own push service, or clear the field to turn push off. The privacy policy has the details.

Never for dark chats, view-once photos or message requests: those only say “New message” or “Message request”, without the sender’s name or text. Push wake-ups never contain content either. When the app itself finds a new message in an ordinary chat during a background check, it can show a preview on your lock screen; you can turn previews off for Nullchat in the system notification settings.

1. Open the Nullchat web app in a browser, or the Mac app. It shows a QR code.
2. On your phone: Settings → Linked devices → Link a device, and scan that code.
3. The computer now shows a 6-digit code. Type it on your phone. Choose whether to include recent messages (text from the last 30 days), then tap Link device.

You can link up to 4 browsers or Macs. Each gets its own key, so your identity key never leaves the phone. To remove one, use Settings → Linked devices on the phone, or Unlink this browser on the device itself. On a Mac you can also install the web app with Safari’s File → Add to Dock.

Dark chats and view-once photos are phone-only by design. Linked devices also only receive messages sent after they were linked, plus the optional 30-day text history.

Yes. Any Nostr relay that accepts events of 256 KB and supports NIP-40 expiry works; strfry is a good choice. Add wss://your.host in Settings → Relays. The app tests that the relay can store and return messages and tells your contacts to use it. Instructions: docs/self-host-relay.md.

Yes. The push service is a small stateless program in apps/push-worker that runs as a Cloudflare Worker or a Docker container. It needs Apple and Firebase credentials that match the app build, so in practice you run it together with your own build of the app, then paste its URL in Settings → Notifications.

Yes, it’s AGPL-3.0. Start with the README and ARCHITECTURE.md.

• One tick means at least one relay accepted the message. Two ticks mean it reached the other person’s device. It’s marked read when they’ve seen it (if they have read receipts on).
• Check Settings → Relays: at least one relay should show as connected. If you’re on a network that blocks WebSocket connections, try another network.
• The other person must have accepted your request. Until then your messages wait in their Requests.
• If no relay accepts a message, the app keeps retrying for 24 hours. After that it shows as failed, and you can tap it to retry. Delivered messages wait on relays for up to 7 days for the other person to come online.

Settings → Delete everything erases your key, contacts and messages from the phone and tells contacts to stop writing to you. Write down your backup phrase first if you might want this identity back.