Witness
btc · transaction
In SegWit transactions, the witness is the separate field that carries signatures and other unlocking data.
The witness contains data needed to satisfy spending conditions, such as signatures and public keys, but is separated from the legacy transaction serialization. This design reduces common transaction malleability issues.
SegWit changes fee accounting by using transaction weight, where witness data is discounted compared with non-witness data. This is why wallets often quote fees in satoshis per virtual byte.
Related terms
SegWit
→A Bitcoin upgrade that moved signatures into witness data, fixing third-party malleability and changing block capacity.
scaling · btc
Signature
→A cryptographic proof that a message was authorized by the holder of a private key.
cryptography
Transaction
→A serialized state transition that a blockchain can validate, relay, and include in a block.
blockchain · technical