BIP 49
Derivation scheme for P2WPKH-nested-in-P2SH based accounts
Original title: Derivation scheme for P2WPKH-nested-in-P2SH based accounts
- Status
- Deployed
- Type / Layer
- Specification / Applications
- Author
- Daniel Weigl
- Assigned
- Status verified
- Source
- github.com/bitcoin/bips/blob/master/bip-0049.mediawiki
Summary
Defines the derivation scheme for SegWit addresses used in their P2SH-nested form (P2WPKH-nested-in-P2SH). Setting purpose to 49' keeps BIP44's hierarchy while separating SegWit accounts from legacy ones. The separation exists to avoid a confusing recovery failure: if the same seed is loaded into a wallet that does not implement this scheme, an account that shows up but is missing some of its UTXOs would make the user believe funds had gone. With a distinct purpose, an incompatible wallet simply does not show the account at all, so whatever it does show is correct. The nesting itself is for backward compatibility: hashing the witness program into a P2SH address means software that knows nothing about SegWit can still pay it as an ordinary address starting with "3", letting the receiving side migrate first. Extended keys use their own version bytes (ypub / yprv on mainnet) rather than xpub / xprv.
Why it matters
It provided the migration path that let the receiving side benefit from SegWit without waiting for senders to support it. Now that native SegWit (BIP84) is widely payable there is little reason to choose it for new accounts, but addresses created this way remain in use and wallets still scan this path for recovery compatibility.
Related BIPs
Related articles
This page carries a summary, not a translation. The original document is authoritative, and the metadata above — including Status — was transcribed from the bips repository on the verification date shown. Always consult the original when implementing or verifying.