What is a Bitcoin timelock?

A timelock makes an output unspendable until the chain reaches a set height or timestamp. Wallets show the coins but cannot move them early — the rule is enforced by nodes, not by the wallet.

Payment channelsPayment channelA shared pot of bitcoin between two parties on the blockchain, which they can pay each other from, off-chain, as often as they like., vaults and inheritance setups use timelocks, as do some multisigMultisig (multi-signature)A wallet whose coins need signatures from several keys, such as 2 of 3, so no single key can spend alone. recoveries. If your wallet says funds are locked until a block or date, a timelock is why; they unlock by themselves when it passes.