A marker over
your stack.
Bitcoin-only widgets and a dashboard that keeps watch over your cold storage. Watch-only by design — keys never enter the app. Free, and collects nothing by default.
Sideload it. 11.2 MB · Android 8.0+
Not on the Play Store yet.
Bitcoin, right now.
connecting…A glance at what Cairn puts on your homescreen: price, network, and the Cycle Lab, read live from the same sources the app uses. Read-only, like everything here.
Updated —. On-chain metrics are daily-close. Not financial advice.
The constraints are the product.
Every other Bitcoin app on Android either launders shitcoins next to your price ticker or wants your keys. Cairn does neither, on purpose.
Bitcoin only
No shitcoins, ever. The signal is what's left when you remove everything that isn't Bitcoin.
No accounts, no KYC
No sign-up. No backend that knows your name. Everything stays on your device.
Watch-only
Cairn can watch but never spend. Read-only, always. Nothing here could move a single sat.
Point at your own node
Override every data endpoint and point Cairn at your own node. Free of API gatekeepers.
It keeps watch on your cold storage.
Add an xpub, an output descriptor, a single address, or a Lightning wallet over NWC. Cairn watches it and tells you the moment it moves, especially when you didn't move it. Read-only, so it can watch but never touch.
Watch anything
An xpub or descriptor, a single public address, or a Lightning wallet via NWC. Whatever you want an eye on, in one list.
Hidden, if you want
Tell a wallet never to show its balance: not in the app, not on the widget, not even behind the eyeball. It still watches. It still alerts. The number just stays yours.
The moment it moves
Alerts on any change, up or down. There's also a spend alert that fires the instant an outgoing transaction hits the mempool, before it confirms. An unexpected spend is worth checking on.
On your phone, in your inbox
A notification with sound, an email, or both. Email, if you switch it on, sends a bare "a wallet changed" note and nothing more.
What you watch is encrypted on the device with the Android Keystore and never leaves it. There's no account, and no Cairn server holding your wallets. Turn email alerts on and the only thing that ever leaves is the email address you verify and a bare "a wallet changed" note: never which wallet, the amount, or the bitcoin address. Leave email off and nothing leaves the phone.
Sideload it in three steps.
You're installing outside the Play Store, so Android will ask for permission once. This is normal for a beta.
Download the APK
Tap the download button on your Android phone. The file lands in your downloads folder.
Allow the install
Android will ask whether to allow installs from this source. Say yes, just this once.
Open Cairn
Tap the file, install, then pin your first widget. The cairn is just stones until you start.
Don't take our word for any of it. The full source is public — read it, rebuild it, and check what you downloaded. Three ways, strongest first.
A signed F-Droid build, verifiable independently, is planned for a later release.
Set your marker on the homescreen.
v0.9.10 · beta · 11.2 MB · Android 8.0+
Free. No ads, no analytics, no KYC.