Timelock
A condition under which bitcoin may only be spent from a certain block height or point in time, or after a waiting period. Timelocks are a building block for Lightning and for inheritance and emergency setups.
Alsotime locklocktimenLockTimeCLTVCheckLockTimeVerifyCSVCheckSequenceVerify
On the learning path: Stage 6 · Step 4 – Inheritance & emergency plan
A timelock specifies that bitcoin may only be moved from a certain moment onwards. Nodes enforce this: a transaction that comes too early is invalid – no matter who signs it.
Absolute or relative
- Absolute: until a fixed block height or point in time. Every transaction has an
nLockTimefield for this: values below 500 million count as a block height, values of 500 million or more as a Unix timestamp.[1] - Relative: counted from the confirmation of the coins being spent – for example ‘no earlier than 1,000 blocks later’.[2]
With BIP 65 (CLTV) and BIP 112 (CSV), such locks can be written directly into the spending conditions.[3],[2]
What timelocks are used for
- Lightning: in payment channelsGlossaryPayment channelA shared bitcoin pot between two parties, secured by a 2-of-2 multisig address. Within the channel, both shift balances by signing a new channel state, without writing every payment to the blockchain.In the glossary →, timelocks give the cheated party time to respond to an outdated channel state, and they secure forwarded payments.[4]
- Inheritance and emergencies: normally only you can spend – but after a long period without activity, a backup key can too, for example one for relatives. If you move the coins in time, say to a new address in the same wallet, the clock starts again.[2]
Related terms
These terms are closely connected.
- This termTimelock
- Payment channelA shared bitcoin pot between two parties, secured by a 2-of-2 multisig address. Within the channel, both shift balances by signing a new channel state, without writing every payment to the blockchain.
- Lightning NetworkA second layer on top of Bitcoin for fast, low-cost payments. Amounts move off the blockchain via payment channels; only opening and closing a channel ends up in a block as a normal transaction.
- Multisig (multi-signature)A wallet in which several keys jointly control the bitcoin – for example 2 of 3. If one key is lost or stolen, the bitcoin stays safe. In return, setting it up and backing it up is considerably more demanding.
- TransactionA signed message that transfers bitcoin from existing outputs (UTXOs) to new outputs. It only counts as confirmed once it is in a block – and after that it can practically no longer be reversed.
- BlockA bundle of transactions added to the blockchain roughly every ten minutes on average. Each block refers to its predecessor by its hash and contains the reward for the miner.
Explained in depth
These articles go into more detail:
- Deep dive · Stage 1Lightning NetworkHow payment channels and routing work, what Lightning is good for, where its limits lie and what to look out for with Lightning wallets.
- Stage 6 · Step 4Inheritance & emergency planHow your family can reach your bitcoin if the worst happens: an emergency letter without the seed phrase, separate storage, and German law and tax in brief.
- Deep dive · Stage 6MultisigWhat a 2-of-3 multisig wallet is, who it’s worth it for, how to set it up and why you need to back up the descriptor as well as the seeds.
More from „Technology“
Sources4 sources · 2 publishers
The superscript numbers in the text refer to these sources.
- Bitcoin Developer Guide: Transactions – bitcoin.org Developer Documentation (accessed 28/09/2026)
- BIP 112: CHECKSEQUENCEVERIFY – Bitcoin Improvement Proposals, 10.08.2015 (accessed 28/09/2026)
- BIP 65: OP_CHECKLOCKTIMEVERIFY – Bitcoin Improvement Proposals, 01.10.2014 (accessed 28/09/2026)
- BOLT #3: Bitcoin Transaction and Script Formats – Lightning Network Specifications (BOLTs) (accessed 28/09/2026)
This entry is for education only and is not investment, tax or legal advice.