The Genesis of Segregated Witness (BIP-141)
Activated in August 2017 following intense industry debate, SegWit resolved one of Bitcoin's oldest architectural vulnerabilities: transaction malleability. By separating signature data (the witness) from the transaction ID calculation, SegWit prevented malicious nodes from altering transaction hashes before confirmation.
The Weight Unit & Fee Discount:
SegWit introduced the concept of Virtual Bytes (vB) and gave witness data a 75% discount in block space pricing. A native SegWit transaction (bc1q...) costs up to 40% less in miner fees than an older legacy transaction (1...).
The Power of Exchange Transaction Batching
During peak congestion in late 2017, exchanges that processed customer withdrawals individually generated massive mempool backlogs. By batching 100 customer withdrawals into a single multi-output transaction, exchanges save up to 80% on total block space, keeping network fees reasonable for all users.
Address Format Migration Checklist
- Legacy (1...): Inefficient; avoid using for modern Bitcoin transactions.
- Nested SegWit (3...): Compatible with older wallets; provides partial fee discount.
- Native SegWit Bech32 (bc1q...): Industry standard for lowest transaction fees and optimal error detection.