A Bitcoin upgrade that separates signature data and introduced block weight accounting.
Segregated Witness (SegWit) meaning
SegWit changed how transaction witness data is committed and measured. It fixed transaction-ID malleability for SegWit spends, increased effective transaction capacity, and made more efficient output types possible.
How it works in Bitcoin
SegWit transactions place unlocking witness data in a separate structure while committing to it through the block. Block limits use weight units, where witness bytes count differently from non-witness bytes.
A simple example
A native SegWit receive address commonly begins with bc1q. Spending from that output often uses less block weight than an older equivalent, which can reduce fees at the same fee rate.
Why Segregated Witness (SegWit) matters
Transaction terms matter whenever bitcoin moves. Understanding them reduces mistakes involving fees, confirmation status, change outputs and irreversible destinations.
What people often get wrong
SegWit did not simply raise the old one-megabyte serialized block limit to one fixed megabyte number. Weight and serialized size are different measurements.
Quick checks before using the term
- Is the transaction only broadcast or already confirmed?
- Which outputs and fee are being created?
- Can wallet policy replace or delay it?
Apply these questions to the concrete example above. A precise answer is more useful than repeating the definition without naming the actor, rule or failure path.
Check the primary reference
This entry is written in plain English, but the technical source is available when you need exact protocol detail.
BIP 141: Segregated Witness ↗