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CSV - CheckSequenceVerify (BIP-68/112/113)

   
Year 2016
Type Soft fork (MASF)
BIPs BIP-68, BIP-112, BIP-113
Status Active

What it does

Three related BIPs that enable relative time locks:

  • BIP-68: Redefines the sequence number field to encode relative lock-time constraints
  • BIP-112: Adds OP_CHECKSEQUENCEVERIFY opcode for script-level relative time locks
  • BIP-113: Uses median-time-past for time-lock calculations (more robust than block timestamps)

Why it mattered

  • Enabled bidirectional payment channels (critical for Lightning Network)
  • Allowed contracts that say “this output can’t be spent until N blocks after it was confirmed”
  • Complemented CLTV’s absolute time locks with relative ones
  • Direct prerequisite for Lightning Network deployment

How it activated

Miner-activated soft fork using BIP-9 versionbits signaling. Required 95% of blocks in a retarget period. Activated in July 2016.

Outcome

Smooth activation, no chain split. Together with CLTV, CSV completed the time-lock infrastructure needed for the Lightning Network.