SegWit
TL;DR
Segregated Witness (SegWit) is a Bitcoin upgrade from August 2017 that separated signature data from transaction hashes, enabling lower fees and solving malleability.
SegWit moved signatures ('witness') into a separate structure, solving three issues: fees dropped as witness bytes count only 1/4, transaction malleability was fixed (prerequisite for Lightning), and block capacity effectively rose to ~4MB weight. Native SegWit addresses start with bc1q...
Example
A legacy tx of 225 bytes at 20 sat/vB → 4,500 sats. Same tx in SegWit: ~141 vbytes → 2,820 sats. A 37% saving for every migrated user.
Frequently asked questions
What % of the network uses SegWit?
In 2026 around 85-90% of all transactions. Legacy addresses are slowly dying out.
Related terms
Further reading
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