the prefix xprv9s21ZrQH143K...? no matter which seed phrase I start from. whereas normal private keys will vary totally.

What does the "...9s21ZrQH143K..." mean? Further, this sequence will sometimes be followed by a 3 or a 4, but often times it's a 2 before continuing the rest of the string.

I searched all over the web and couldn't find an answer.

1 Answer 1


The xprv format contains some metadata about the key it contains.

Part of that metadata is what level from the root it is (an xprv can be derived from another xprv, incrementing the level by one). Another piece of metadata is what the (32 bit) fingerprint of the parent it is derived from, if any.

Root xprvs (those directly derived from a seed) have level 0, and parent fingerprint 00000000. When converting to base58 format, those 5 bytes for level + fingerprint translate to a fixed string.

  • Thank you, that makes sense now! Particularly the part about the default parent fingerprint value being 00000000 for every master key pair... thx
    – bitguy54
    Jun 21, 2023 at 6:03

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