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An impact report from the front-lines of nostr developer libraries.
Bech32
Bech32m, bc1, bc1q, bc1p, native SegWit address
The checksummed base32 address format used for native SegWit outputs. Version 0 uses bech32 and version 1+ uses bech32m.
Bech32 is the checksummed base32 format introduced in BIP 173 for native SegWit addresses. On mainnet those addresses start with bc1, which is why people often call them bc1 addresses. The format avoids mixed case, uses a character set that works well in QR codes, and includes a checksum that catches almost all common typing errors.
Version 0 witness outputs use the original Bech32 checksum. Those are the bc1q... addresses used for P2WPKH and P2WSH. When Taproot introduced version 1 witness outputs, Bitcoin adopted Bech32m through BIP 350. Those bc1p... addresses keep the same structure and character set but use a different checksum constant that fixes a weakness in the original design for future witness versions.
In practice, Bech32 and Bech32m are one address family. Wallets need to decode both, enforce the right encoding for each witness version, and reject mixed-case or malformed strings. The distinction matters because version 0 outputs remain valid only under Bech32, while Taproot and later witness versions require Bech32m.