P2WSH

P2WSH, or Pay to Witness Script Hash, is a type of Bitcoin script that locks coins to the hash of a witness script. In a P2WSH output, the scriptPubKey uses a SegWit version 0 witness program, which effectively commits to the 32-byte hash of a redeem (witness) script rather than the script itself.

To spend a P2WSH-output, a transaction must provide a witness that contains two parts: the witness script itself and the data required by that script. Nodes verify that sha256(witnessScript) equals the hash embedded in the scriptPubKey, then execute the witness script with the provided arguments. If the script evaluates to true, the spend is valid. The actual script code is not revealed until spending, which distinguishes P2WSH from non-SegWit scripts and helps reduce malleability.

P2WSH is a native SegWit alternative to P2SH (Pay to Script Hash). While P2SH stores the hashed redeem script in the scriptPubKey and reveals it during spending, P2WSH places the script into the witness data, with the scriptPubKey containing only the version and the hash. This separation allows for more efficient block space usage and, when combined with SegWit, lower transaction weight. P2WSH can be used directly (Bech32 addresses) or wrapped inside P2SH for compatibility with older wallets that lack SegWit support.

Common use cases include complex multisig arrangements, timelocks, and other sophisticated spending conditions where the script is large or frequently changing. As with all Bitcoin scripts, correct construction and validation of the witness script are essential for security.