BIP-139 GIVES BITCOIN WALLETS ONE EXPORT FORMAT — IT BARS MAINNET SEED WORDS BECAUSE BACKUPS MAY SIT IN THE CLOUD — EVERY VALID FILE MUST CARRY A DESCRIPTOR AND ENCRYPTION IS OPTIONAL

On October 24, 2026, the bitcoin BIPs repository merged BIP-139, a draft standard for exporting everything a wallet knows except the keys: accounts, descriptors, signers, labels, transactions, coins and transactions still waiting on signatures. The author, who goes by Pyth, posted the first draft to the bitcoindev list on March 27. The pull request ran 92 commits. The goal is to end lock-in, so what one wallet writes another can read.

The rule on keys is blunt. The format “MUST NOT include mainnet secret signing keys or mnemonics, since an export kept as a backup may be stored online or in cloud storage.” The seed-word field is for test networks only, and a seed with a passphrase can’t use it at all. Good. Nobody can spend your coins from one of these files.

But read that reason again. The authors expect these files to sit in the cloud, and the smallest valid file still has to hold each account’s descriptor. For a normal wallet, the descriptor lets anyone work out every address it has used and every address it will use. Add the optional coins, labels and transactions and it’s your whole history in one file. A silent payments descriptor may even carry the private scan key, which the BIP allows on mainnet.

Encryption is a can, not a must: the format “can be encrypted following BIP-138.” The security notes warn about seed words and private app data, not about the descriptor. Nobody can spend from this file, but anyone who reads it can watch you. Your keys keep your coins. Your backups keep your privacy, or they don’t. The BIP is still a draft, and its reference implementation reads TBD. At the time of this writing, bitcoin was $80,401.