Which Bitcoin Improvement Proposal introduced native SegWit bech32 addresses? BIP 173 introduced the Bech32 format for native SegWit addresses.
Published in 2017, BIP 173 specifies a checksummed Base32 encoding for native witness outputs, including the familiar mainnet addresses beginning with “bc1.” It was authored by Pieter Wuille and Greg Maxwell and was later deployed in Bitcoin Core.
Several nearby BIPs are easy to confuse. BIP 141 defined Segregated Witness itself, while BIP 143 specified a new transaction-signing algorithm for SegWit. BIP 174 defines Partially Signed Bitcoin Transactions, or PSBTs. BIP 350 later introduced Bech32m, a related format used for newer witness versions such as Taproot.
Bech32 improved on older Base58Check addresses by using a case-insensitive character set, a structured human-readable prefix, and a strong checksum. Native SegWit v0 addresses therefore use BIP 173’s Bech32 rules, while newer witness versions generally use Bech32m.