I've seen extended public keys such as the one below


But now I've seen a bpub


What's the difference?

  • I don't recall this being defined in any (common) spec. Where are you seeing this? Commented Aug 16, 2018 at 17:58
  • bpub is probably the prefix for extended public keys for an altcoin.
    – Ava Chow
    Commented Aug 16, 2018 at 18:15
  • @RaghavSood I found it while trying to answer a question about pywallet - and thus extended keys. github.com/Ballanxe/pegaso/blob/…
    – arshbot
    Commented Aug 16, 2018 at 19:20
  • 1
    @AndrewChow can you elaborate? What are prefixes? When do they apply? Why are they the same for some altcoins but not others?
    – arshbot
    Commented Aug 16, 2018 at 19:21

1 Answer 1


bpub appears to be the extended private key prefix for the Blockcypher testnet.

Bitcoin addresses and private keys usually have a prefix to help differentiate the network/type of key.

The original xpub notation comes from BIP32, meaning extended public key. This expanded into ypub with BIP49, and finally zpub with BIP49+ (used in BIP84).

Various coins can define their own prefix by simply altering the bytes. Litecoin, for instance, often uses Ltub.

It works the same way as changing the address prefix, except you change four bytes, instead of one.

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