A USB stick that turns a computer you already own into an offline Bitcoin signing device. While it is running, that machine cannot go online and cannot see its own hard drives. Switch it off and everything you did is gone.
Any PC or old laptop with a USB port becomes an offline signing device for as long as it is switched on: write one image to a stick, start the machine from it, and create a wallet whose recovery words never touch anything connected. Nothing is installed, your disks are never read, and taking the stick out leaves no trace.
See all three flows, screen by screen → A PRESENT SOMEBODY CAN HOLDMake the wallet on a machine that cannot go online, write its words onto a printable A4 card by hand, and hand it over closed. The card carries a QR to a page that tells the person you gave it to exactly what to do next — whether they want to spend it or keep it.
Print a gift card →SignerOS starts from a USB stick and runs entirely in the computer's memory. It has no way to reach the internet, no way to touch the machine's hard drives, and nowhere to keep a history. The only place it can save anything is the stick you booted from, and the only things it saves there are files that are safe to share — a signed transaction, or the public keys your everyday wallet needs to watch your balance. Switch the power off and the session, your recovery words included, is gone.
See the signing ritual ↓The ability to use a network was left out of this system entirely, so Wi-Fi, Ethernet and Bluetooth do not merely fail — they are not there. There is nothing to switch off, and nothing to remember to switch off.
The whole system lives in memory and never installs itself. It cannot even see the hard drives of the machine you borrowed, so what is on them cannot be read, changed or infected. Nothing is written anywhere except, when you ask for it, one file on your own stick.
The stick boots straight into the signer and there is nothing else on it: no desktop, no browser, no file manager, no command line. Fewer moving parts means fewer places for something to hide, and far less code for anyone to check.
Any reasonably modern PC with a USB port becomes a signer for as long as it is switched on — an old laptop is ideal. Take the stick out, start the machine normally, and it is as if SignerOS was never there.
There is one app on the stick and its first screen offers exactly those three choices. There is no desktop behind it, no browser, no file manager and no command line — the signer is the whole of what the machine can do until you switch it off.
Your everyday machine prepares the transaction; the offline machine approves it. The only thing that travels between them is a file on a USB stick — the SignerOS stick itself does fine. There is no camera and no QR scanning here, and nothing that crosses ever contains a secret.
In your everyday wallet, build the payment as usual and save it as an unsigned transaction file instead of sending it.
ONLINE PCCopy that file onto the stick. Any name will do as long as it ends in .psbt. Nothing on this stick is secret at any point.
Start the offline computer from the stick. The app lists the transaction files it finds and you pick the one to look at.
SIGNEROSWho gets paid, how much, and what the fee is — all worked out from the file itself rather than taken on trust. Read it like a receipt.
SIGNEROSType your recovery words. The machine shows you one last summary in plain terms — what is really leaving your wallet, what is coming back — you confirm, and it signs. Your key is erased immediately afterwards.
SIGNEROSThe signed file is saved next to the original, which is left untouched. Use Secure shutdown and wait for the machine to switch off before pulling the stick out.
SIGNEROSTake the stick back to your everyday machine and send the signed transaction from there. Done — nothing secret ever left the offline machine.
ONLINE PCSignerOS can hold the single key to a wallet — or be one signature of several, alongside a hardware wallet you already own. The same stick does both: it hands your everyday wallet the public keys it needs, and signs whatever that wallet passes back. Setting one up is a walkthrough of its own: two SignerOS seeds into one 2-of-2 in Sparrow, a payment signed twice, and broadcast.
Your everyday wallet, set up from the public keys SignerOS exported. It can watch your balance and prepare payments — but it cannot send one.
Your personal computer, booted from the SignerOS USB. Reviews and signs. Never online — it has no way to be.
One key, kept offline. Only the offline machine can approve a payment, and only while it is switched on. Everything else stays an ordinary, everyday computer.
Software like Sparrow puts the three devices' public keys together into one wallet, prepares the payment, and collects signatures until it has enough.
Key #1. A personal computer booted from the SignerOS stick.
Key #2. A second, separate personal computer — ideally kept in another place.
Key #3. Any hardware wallet that can sign transaction files completes the trio.
Any two of the three. Two signatures approve a payment, so one lost key is survivable and one stolen key is useless on its own. One thing to know: with a setup like this, your recovery words alone are not enough to get your money back — you also need the file that describes the wallet, including the other two devices' public keys. Back that file up somewhere alongside your words. It cannot spend anything, so keeping copies of it is safe.
Every flow in section 02 ends with a set of words that exist nowhere but on paper, and one of them ends with a wallet you can hand to somebody else. These three pages are the paper half of that: single HTML files that fetch nothing, so you can open them on the offline machine, print them blank, and fill them in with a pen.
Numbered lines for 12 to 24 words, the master fingerprint the machine showed you, and a passphrase reminder that deliberately keeps the passphrase off the sheet. The back explains in five steps what the machine does with them.
Print it → A4 · BIRTHDAY / WEDDING / ANYA wallet you can give away: pick the occasion, type the name and a short note, print it blank and write the words inside by hand. The face carries no product name at all — it is a gift, not an advert.
Make one → WEB PAGE · FOR THE RECEIVERWhat to do when somebody hands you one, starting from the fact that its words are not a secret any more: one decision — spend it or keep it — then the steps on a phone for either, and the fully offline route where the words never touch a machine that can go online.
Read it →// Whichever one you print, the words are written by hand. None of these pages has a field to type them into and none of them ever will: a typed seed is a seed in an undo buffer, an autofill store and a print spool at once.
The nicest way to try SignerOS end-to-end: make your very first signed transaction a small one to the donation address below. A few thousand sats is plenty — and it proves the whole loop works on your machine before anything that matters depends on it. Prefer Lightning, or want to know what a donation does and does not buy? That is all on the donation page.
DONATION ADDRESS · BITCOIN ON-CHAIN
// Bitcoin on-chain only, on Bitcoin's own network. Every sat is a thank-you — there are no tiers, no perks, just the project moving forward.