BIP39 Seed Derivation
Paste a BIP39 mnemonic recovery phrase to validate it and derive the 512-bit BIP39 seed (PBKDF2-HMAC-SHA512) your wallet uses. Runs entirely in your browser — nothing is sent to a server.
About this tool
This tool takes a BIP39 mnemonic recovery phrase you already have and derives the 512-bit BIP39 seed — the master secret that Bitcoin and virtually every modern hierarchical-deterministic (HD) wallet expand into every private key (BIP32 / BIP44). Before deriving, it checks that the phrase is a valid BIP39 mnemonic: the right word count, every word in the official 2048-word English list, and a passing checksum. Need to create a brand-new phrase instead? Use the BIP39 mnemonic generator.
How it works
- Validate — the phrase is normalized (lowercased, whitespace collapsed) and
checked: it must be 12, 15, 18, 21, or 24 words, every word must exist in the
BIP39 English wordlist, and the trailing checksum bits — the first ENT/32 bits
of
SHA-256(entropy)— must match. Any failure is reported instead of a seed. - Recover entropy — each word maps to an 11-bit index; the leading bits reconstruct the original 128–256 bits of entropy shown in the output.
- Derive the seed — the mnemonic plus your optional passphrase is stretched
with
PBKDF2-HMAC-SHA512(2048 iterations, salt"mnemonic"+ passphrase) into the 64-byte (512-bit) seed.
Options
- Mnemonic phrase — paste your 12–24 word BIP39 phrase. Case and stray spaces are tolerated; unknown words and bad checksums are rejected with a clear message.
- Passphrase — the optional BIP39 "25th word." It never changes the words, but it is mixed into the derivation, so the same phrase with a different passphrase produces a completely different seed (and therefore a different wallet).
Privacy
Everything runs locally in your browser via WebAssembly. Your mnemonic, passphrase, and the derived seed never leave your device. Never paste a phrase that guards real funds into any website you do not fully trust — prefer an offline machine or a hardware wallet for anything of value.
FAQ
What is the difference between the mnemonic, the entropy, and the seed?
The entropy is the original 128–256 random bits. The mnemonic is those
bits (plus a checksum) encoded as 12–24 memorable words. The seed is a separate
512-bit value produced by running the mnemonic and an optional passphrase through
PBKDF2-HMAC-SHA512. Wallets store or back up the mnemonic, but they derive all
keys from the seed. This tool shows all three so you can verify a recovery.
Why was my phrase rejected as invalid?
Three things must hold for a BIP39 phrase: it has exactly 12, 15, 18, 21, or 24 words; every word appears in the BIP39 English wordlist; and the built-in checksum passes. A rejection usually means a word is misspelled, a word is in the wrong position, or a word is missing or duplicated. The error names the failing word or the specific rule so you can fix it. Only the English wordlist is supported.
Does the passphrase change the words or just the seed?
Only the seed. The passphrase (the "25th word") is never part of the mnemonic and never alters the words — it is folded into the PBKDF2 stretch, so the same 12–24 words with a different passphrase yield a completely different 512-bit seed and therefore a different wallet. If you lose the passphrase, the words alone cannot restore that wallet, so record it as carefully as the phrase itself.
Can I check this against a known BIP39 test vector?
Yes. The canonical Trezor vector is the phrase abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about with passphrase
TREZOR, which derives the seed
c55257c360c07c72029aebc1b53c05ed0362ada38ead3e3e9efa3708e53495531f09a6987599d18264c1e1c92f2cf141630c7a3c4ab7c81b2f001698e7463b04.
The BIP39 test vector (TREZOR) example chip loads exactly this so you can
confirm the output matches.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool bip39-seed-derive "abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about"New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/bip39-seed-derive/?mnemonic=abandon%20abandon%20abandon%20abandon%20abandon%20abandon%20abandon%20abandon%20abandon%20abandon%20abandon%20about&passphrase=leave%20blank%20for%20noneMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.