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What is multisig?
Multisig (multi-signature) is a setup where moving funds needs approval from several keys instead of one, for example any 2 of 3. Each key can be held on a different device or by a different person.
What it means for you
One stolen or lost key is not enough to move or lose the funds, but losing more keys than the setup can spare locks them permanently. Record which keys exist, who holds each, and the full wallet setup needed to restore it, not only the seed phrases.
How it works
A multisig output is locked to n public keys and a threshold m: spending needs valid signatures from any m of them. BIP 11 made m-of-n with up to three keys a standard transaction using OP_CHECKMULTISIG; today such scripts are usually wrapped in pay-to-script-hash, where the sender pays to a hash of the script and the spender reveals the full script when spending. Spending therefore needs every public key and the exact script, not just m seed phrases. BIP 11 cites 2-of-2 for a co-signing protection service and 2-of-3 for escrow with a dispute agent.
An example
Say you set up a 2-of-3 wallet: one key on a phone, one on a hardware wallet, one in a bank deposit box. Lose the phone and you can still spend with the other two. Lose two of the three, and the coins cannot be moved by anyone.
Sources: BIP-11: M-of-N standard transactions, bitcoin.org: Secure your wallet, Bitcoin developer guide: Transactions · checked 4 October 2026
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