BIP39 Mnemonic Generator

Generate and validate BIP39 mnemonic seed phrases (12/18/24 words) with entropy and seed hex — client-side only.

Client-side

About this tool

The BIP39 Mnemonic Generator creates cryptographically random mnemonic seed phrases following BIP39 (Bitcoin Improvement Proposal 39), the standard used by essentially every modern cryptocurrency wallet to represent a wallet's master seed as a human-readable, memorizable list of words drawn from a fixed 2048-word list.

Choose 12, 18, or 24 words, corresponding to 128, 192, or 256 bits of entropy respectively. Alongside the mnemonic, the tool shows the raw entropy in hex and the derived seed in hex (the PBKDF2-HMAC-SHA512 stretched output of the mnemonic plus an optional passphrase, which is what wallet software actually uses to derive keys via BIP32/BIP44). Changing the passphrase live-updates the derived seed so you can see exactly how a passphrase — sometimes called a "25th word" — produces a completely different wallet from the same mnemonic.

A separate Validate section lets you paste any mnemonic and checks it against the BIP39 checksum: the last word of a valid mnemonic encodes a checksum of the preceding entropy, so a single mistyped or reordered word is almost always detected as invalid.

All generation and validation runs entirely in your browser — no network request is made, and nothing is stored, logged, or persisted beyond the current page session.

FAQ

Is it safe to generate a real wallet mnemonic with this tool?

No. Never use any online tool to generate or enter a mnemonic for a wallet holding real funds. Use a dedicated hardware wallet or well-audited offline software. This tool is for education, testing, and development against non-financial or testnet systems.

What is the difference between the mnemonic, entropy, and seed?

Entropy is the raw random bits generated first. The mnemonic is that entropy plus a checksum encoded as words for human readability. The seed is a further PBKDF2-stretched value derived from the mnemonic and an optional passphrase — wallets feed the seed, not the mnemonic directly, into BIP32 to derive keys.

What does the passphrase (25th word) do?

An optional passphrase is mixed into the PBKDF2 derivation that produces the seed. The same mnemonic with different passphrases produces entirely different wallets — losing the passphrase means losing access to funds derived with it.

Why does validation say a mnemonic is invalid even though all the words are real BIP39 words?

BIP39 mnemonics encode a checksum in their final word, derived from the preceding entropy. An incorrect word order or a single wrong word will almost always fail the checksum, correctly flagging the phrase as invalid.

Does this tool support wordlists in languages other than English?

This tool currently generates and validates against the standard English BIP39 wordlist, the most widely used and broadly compatible list across wallet software.