BIP 173 — Base32 address format for native v0-16 witness outputs

BIP 173 (Base32 address format for native v0-16 witness outputs) defines bech32, the checksummed, case-insensitive address format for native SegWit outputs (bc1q...). Its checksum was later found to have a weakness for future witness versions — certain insertions could go undetected — which motivated the bech32m variant (BIP 350) for v1+ outputs. Repository status: Deployed.

Debate relevance: Appears in adoption discussions ('exchanges were slow to support bc1 addresses') and as the setup for why Taproot needed a modified format. Common misstatements: "Bech32 is SegWit" — it is an address encoding; SegWit is the consensus change (BIP 141). "Taproot addresses are bech32" — they are bech32m (BIP 350). The checksum weakness allowed certain malleations for future versions; it did not make v0 addresses unsafe.