Glossary / Addresses & keys
BIP-44 purpose level
- What is the BIP-44 purpose level?
- The BIP-44 purpose level is the first number in an HD derivation path, hardened and fixed at 44', which claims the whole subtree beneath it for one wallet standard.
Specified in BIP-44.
Purpose is the first of five levels BIP-44 defines under the master key, and BIP-43 reserves the slot so incompatible wallet layouts never share a tree. BIP-44 fixes the value at 44', written 0x8000002C, and the specification was assigned on 24 April 2014. Open a wallet on the wrong purpose and it rebuilds different addresses from the same seed, reports zero, and leaves your coins on the chain.
How it works
The purpose level is the hardened index directly under the master key, and BIP-44 pins it to the constant 44'. Everything below belongs to that standard, in a fixed five level shape: m / purpose' / coin_type' / account' / change / address_index. The 44 is the BIP's own number, which is what BIP-43 recommends.
What the level declares is narrower than most people assume. BIP-44 says only that the constant "indicates that the subtree of this node is used according to this specification". No address format is named anywhere in the document.
Below the purpose, hardening runs for two more levels and then stops.
| Level | Index | Hardened | Selects |
|---|---|---|---|
| purpose | 44' | yes | the standard owning the subtree |
| coin type | 0' | yes | bitcoin, where 1' means testnet |
| account | 0' | yes | one identity, numbered from 0 |
| change | 0 | no | external chain 0, internal 1 |
| address index | 0 | no | the address, counting upward |
So m / 44' / 0' / 0' / 0 / 0 is the first receiving address of the first bitcoin account, and moving the third level to 1' opens a second account that shares no history with it. Only two coin types appear in BIP-44 itself, 0 and 1; the rest live in SLIP-0044, which SatoshiLabs maintains and the BIP defers to.
Where you see it
The purpose level appears in every derivation path a wallet prints, and 44' is the one that means legacy. A path opening with 44' produces addresses that begin with 1, though not because BIP-44 picked that format. BIP-44 predates every alternative, and the rule that a purpose implies an address type arrived later: BIP-49 in 2016, BIP-84 in 2017 and BIP-86 in 2021 each took a purpose value of its own to mark a different script type.
That has a cost you meet at restore time. Because every standard owns a separate branch, the account discovery routine BIP-44 describes runs once per purpose the software supports, and each run scans an external chain until it hits the gap limit, currently set to 20 unused addresses in a row, before giving up. A wallet offering four formats does four sweeps. A wallet offering one does a single sweep, finds no history on its branch, and shows an empty account while the coins sit under a different first number.
In practice the value surfaces in a wallet's account details beside the extended public key, or in the free text field an advanced restore offers. Our Electrum review lists as a drawback that the interface assumes you already know what a change address and a derivation path are, and the purpose is the part of that field to get right first. One fast check: a second level reading 1' rather than 0' is a testnet branch, where nothing is real money.
BIP-44 purpose level vs derivation path
The purpose level is one number inside a path, not the path itself. A path names five levels in order, and swapping only the first, from 44' to 84', hands the same seed to a different standard while the levels below keep the meanings BIP-44 gave them: BIP-84 reuses them unchanged. A path is BIP-44 only when its first level reads 44', and that leading number, not the label printed beside it, tells you which standard built the addresses.