TERM_DEF // UPGRADES_BIPS / BIP_173_BECH32_SPEC
BIP 173
(BECH32 SPEC)
(BECH32 SPEC)
bech32-spec/">BIP 173 (Bech32 Spec). The native SegWit v0 address encoding.
This page sits in the Upgrades & BIPs section — The proposal process and the major upgrades that shaped Bitcoin. Read on for what it is, why it exists, how it works under the hood, and what to watch out for.
This page sits in the Upgrades & BIPs section — The proposal process and the major upgrades that shaped Bitcoin. Read on for what it is, why it exists, how it works under the hood, and what to watch out for.
WHAT_BIP_173_BECH32_SPEC_IS
BIP 173 (Bech32 Spec) — at a glance
UPGRADES
BIP 173 — "Bech32 Spec" is a proposal in the Addresses family, first published in 2017 with status final. The native SegWit v0 address encoding. Its technical mechanism: Bech32 — 32-char alphabet, BCH checksum detecting up to 4 char errors. every "bc1q..." address; also used by Lightning invoices
Why it exists
DESIGN
BIP 173 (Bech32 Spec) exists to solve a specific problem: a human-friendly, error-correcting encoding for SegWit addresses. Without a written, numbered spec, every wallet and node implementer would interpret the requirement differently — and Bitcoin's value depends on every implementation agreeing exactly. BIP-173 is the single source of truth for this concern, so any new client built today can match the behaviour of every client built since 2017.
HOW_IT_WORKS
Mechanism
HOW IT WORKS
Mechanically, BIP-173 bech32 — 32-char alphabet, BCH checksum detecting up to 4 char errors. Adoption today: every "bc1q..." address; also used by Lightning invoices.
1. Author drafts BIP-173 against the BIP-2 template — abstract, motivation, specification, rationale.
2. The text + a reference implementation are posted on the bitcoin-dev list and as a PR to bitcoin/bips.
3. Reviewers tear it apart: ambiguities, security concerns, edge cases, interaction with prior BIPs.
4. Once stable, the BIP editor merges it; it gets a number (BIP-173) and the status "draft" or "proposed".
5. Implementations land in Bitcoin Core / wallets / other clients. For consensus changes: activation parameters chosen.
6. After deployment + adoption, BIP-173 is promoted to "final"; deprecated proposals get "replaced" or "withdrawn".
WORKED_EXAMPLE
BIP-173 — quick reference card
EXAMPLE
BIP number : 173
Title : Bech32 Spec
Area : Addresses
First published: 2017
Status : final
Fork class : no
Motivation : a human-friendly, error-correcting encoding for SegWit addresses.
Mechanism : Bech32 — 32-char alphabet, BCH checksum detecting up to 4 char errors.
Where it shows up : every "bc1q..." address; also used by Lightning invoices.
Read the spec : https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki
KEY_PROPERTIES
OPT-IN
No authority can force a BIP on anyone. Adoption depends entirely on whether the change is genuinely useful.
NUMBERED
Stable numeric reference — BIP-173 means the same thing across every wallet, miner, and node that has read this spec.
NON-CONSENSUS
BIP-173 is not a consensus rule — clients can implement it without coordinating with the network at large.
DEPLOYED
Implementations of BIP-173 are in production. The behaviour is observable on mainnet today.
COMMON_PITFALLS
Things that catch people out
PITFALLS
- Don't confuse "draft" / "proposed" / "final" status — read the BIP header before relying on it in production.
- The BIP number is just an editorial counter — it doesn't imply correctness or stability. Always cross-reference with the latest bitcoin/bips repo.
RELATED_CONCEPTS
Other terms from Upgrades & BIPs — click any to read its page:
TERMINOLOGY_INDEX
TERMINOLOGY
BIP 173 (Bech32 Spec)
The native SegWit v0 address encoding.
Segregated Witness (SegWit, BIP 141)
The 2017 upgrade separating witness-data/">witness data, fixing tx malleability, and introducing weight units.
Taproot (BIP 341)
Tapscript (BIP 342)
Script-language updates accompanying Taproot — new opcodes, removed limits.
Schnorr (BIP 340)
The Schnorr signature spec adopted by Taproot.
BIP Process
The community workflow for proposing, discussing, and tracking changes to Bitcoin.
Soft Fork Activation
MASF (Miner-Activated Soft Fork)
Activation triggered by miner signaling in block versions.