Cold storage doesn’t make a sound
You did the hard part — hardware wallet, seed stamped into steel, coins offline. Here is the part nobody mentions: if that seed ever leaks — a photo of the backup plate, a compromised passphrase, someone who found the safe — the blockchain will not call you. Coins move in silence, and most people discover the vault is empty the next time they open a wallet they haven’t touched in months.
The chain is public. Watching it needs none of your keys. Watchtower does exactly that one job: it watches your addresses and emails you the minute anything moves — and, just as important, sends a weekly “still untouched ✓” heartbeat, so that silence becomes information instead of hope.
How it works
- Point it at an address. Paste any Bitcoin address. Paid plans accept an xpub, derived into up to 50 addresses in your browser — the xpub itself never leaves it. There is no signup: a random manage token stored in your browser is the only credential.
- We watch the chain. Checks run about every 15 minutes on the free tier, about every 2 minutes on paid.
- You get told. Any movement triggers an email with the direction, the amount, and a link to the transaction. Paid plans raise the instant 🚨 OUTGOING alarm — the theft signal. And every week (plus a monthly proof report on paid) you get positive confirmation that nothing has moved.
Free vs. paid
| Free | Paid | |
|---|---|---|
| Watches | 1 address | 1 xpub → up to 50 addresses, derived client-side |
| Check interval | ~15 minutes | ~2 minutes |
| Movement alert | Email + instant 🚨 OUTGOING alarm | |
| Proof of silence | Weekly “still untouched ✓” email | Weekly heartbeat + monthly proof report |
| Alert channels | Email today — Telegram & nostr soon | |
| Price | Free | 7,000 sats / 30 days · 21,000 sats / 90 days (≈ $21) · 70,000 sats / 365 days |
Paying is as identity-free as watching: a Lightning invoice, a prepaid period, no auto-renew, no card, no KYC, no account. When a plan lapses you simply drop back to free behaviour — nothing silently charges you.
What we store — and what we refuse to
This site’s whole editorial rule is don’t trust, verify — and a monitoring service is a trust ask. So here is the complete inventory of what Watchtower keeps:
- The addresses you watch — encrypted at rest with AES-256-GCM. Even our chain-state markers are keyed by hashes of the addresses, never the plaintext.
- Your alert email — the alarm has to go somewhere.
- Nothing else. No name, no login, no KYC, no password, no analytics beyond the site-wide basics.
Retention is deliberately short. Deleting a watch is an instant hard delete. Paid watches that lapse are warned, then purged about 30 days after expiry. Free watches nobody has visited in about 6 months get a warning on their alert channel, then purged. And the exit is built into the pricing itself: don’t trust us — don’t renew, and it stops.
The limits, stated plainly
- Gap limit. Xpub watching covers the addresses derived in your browser at your last visit. If your wallet hands out a fresh address beyond that range, it is not watched until you revisit and re-derive. If you actively receive to new addresses, revisit afterwards.
- Unconfirmed first, confirmed second. An alert can fire on an unconfirmed transaction; a follow-up email tells you when it confirms — or if it doesn’t.
- An alarm, not a shield. Watch-only means we cannot block a theft — nobody can; that is how Bitcoin works. What an alarm buys you is time: to sweep remaining funds off a compromised setup instead of discovering the loss months later.
FAQ
Can you steal my coins?
No — watch-only. We never see keys or seed, and an address alone moves nothing. On paid plans the xpub never leaves your browser; only the derived addresses reach the server, encrypted at rest.
What happens when it fires?
An email with the address, direction, amount, and a link to the transaction. Unconfirmed alerts get a confirmation follow-up. On paid plans an OUTGOING transaction — the theft signal — raises the instant alarm.
Why sats?
No card, no account, no KYC — and prepaid means no auto-renew. The day you stop trusting us, stop paying, and it stops.
What do you store?
Encrypted watched addresses and your alert email. That is the whole list, and deletion is an instant hard delete.
What about the gap limit?
Xpub coverage is a snapshot from your last visit — hand out fresh addresses, then come back and let it re-derive.
Keep the rest of your setup honest
- Bitcoin Self-Custody Score — grade the setup Watchtower is guarding
- Which hardware wallet? 1-minute picker — if the coins aren’t in cold storage yet
- Move Bitcoin off an exchange — first, get coins somewhere worth watching
- Bitcoin address validator — checksum-check an address before you watch (or send to) it