# Timelocks: CLTV and CSV

Timelocks stop bitcoin being spent until a set time. CLTV uses an absolute block or date; CSV counts from when the coins were received. See examples.

Canonical page: https://mybitcoinexplorer.com/learn/timelocks-cltv-csv
Topic: Bitcoin Script
Published: 2026-10-29
Updated: 2026-10-30


## Two kinds of "not yet"
| | Absolute | Relative |
|---|---|---|
| Transaction-level | `nLockTime` | `nSequence` (BIP 68) |
| Script-level | `OP_CHECKLOCKTIMEVERIFY` (CLTV, BIP 65) | `OP_CHECKSEQUENCEVERIFY` (CSV, BIP 112) |
| Meaning | "not before block 900,000" | "not until 144 blocks after this output confirmed" |

> Diagram: An output locked until a given block height — 900000

## CLTV: absolute
~~~
<900000> OP_CHECKLOCKTIMEVERIFY OP_DROP <pubkey> OP_CHECKSIG
~~~
The spending transaction must have a [locktime](https://mybitcoinexplorer.com/learn/locktime-and-sequence) of at least 900,000, and it can't be mined before that block. Useful for savings locks or inheritance plans.

## CSV: relative
~~~
<144> OP_CHECKSEQUENCEVERIFY OP_DROP <pubkey> OP_CHECKSIG
~~~
The input's sequence must say at least 144 blocks (about a day) have passed since the output was confirmed. This is essential for the [The Lightning Network](https://mybitcoinexplorer.com/learn/lightning-network): it gives the other side time to react if someone cheats. See [Closing channels and watchtowers](https://mybitcoinexplorer.com/learn/closing-channels-and-watchtowers).

## Combining with other paths
Timelocks are often one branch of a script: "Alice and Bob together any time, **or** Alice alone after a year". [Taproot](https://mybitcoinexplorer.com/learn/taproot) makes such branches private until used.


## Real uses
- **Inheritance:** "My key now, or my family's key after one year of no movement."
- **Savings lock:** coins that can't be spent before a chosen date.
- **Lightning:** a delay before a closing party can take its funds, so cheating can be punished.
- **Vaults:** a waiting period during which a recovery key can cancel a suspicious withdrawal.

## Careful
A timelock can't be undone. If you lock coins with only a timelock path, there's no way to reach them early, even if you need them.


## Key takeaways

- CLTV locks coins until an absolute height or time.
- CSV locks coins until a delay has passed since confirmation.
- Lightning relies on relative timelocks for safety.

## Common questions

### Can a timelock be cancelled?

Not the lock itself. If the script has another path, such as multiple signers, that path can be used instead.

### What's the longest timelock?

Absolute locks can be years in the future. Relative locks are limited to about 65,535 blocks (over a year) or about 388 days in time units.

### What is the difference between CLTV and CSV?

CLTV locks until an absolute block height or date; CSV locks for a relative period after the coins confirmed.

### Can I use timelocks in my wallet?

Some advanced wallets support timelocked scripts through descriptors and miniscript.

## Related lessons

- [Locktime and sequence](https://mybitcoinexplorer.com/learn/locktime-and-sequence)
- [HTLCs: hash time-locked contracts](https://mybitcoinexplorer.com/learn/htlc)
- [Payment channels](https://mybitcoinexplorer.com/learn/payment-channels)
- [Bitcoin Script](https://mybitcoinexplorer.com/learn/bitcoin-script)