Don't keep your most important secret in one place
A crypto seed phrase, a password manager's recovery key or the code to a safe is risky in one place: lose it and it's gone, or someone finds it and has everything. The secret splitter turns it into several shares. You choose how many are needed to rebuild it, for example any 3 of 5. Give them to people you trust or keep them in different places.
How it works
It uses Shamir's Secret Sharing, a well-studied method from 1979. Fewer shares than the number needed reveal nothing at all about the secret. The maths comes from the open-source shamir-secret-sharing library, which has been independently audited by Cure53 and Zellic.
Each share starts with SSS1 and a set code, so shares from different splits can't be mixed. A short check at the end catches typos, and the rebuilt secret is checked against a fingerprint so a wrong result is never shown as correct.
Questions
Is my secret sent anywhere?
No. Splitting and rebuilding happen in your browser, and nothing is saved. To be extra careful, load this page, turn off your internet connection, then use it.
Do I need this website to rebuild it?
Shares use a standard method and an open-source library, so they can be rebuilt with the same library elsewhere. Keeping a saved copy of this page also works offline.
What should I choose?
3 of 5 is a common choice: you can lose two shares and still recover, and no two people can get together and read it.