BIP39 Mnemonic Converter

Generate a random BIP39 mnemonic seed phrase, or validate an existing one and derive its entropy and 512-bit seed — the same 12-to-24-word phrases used by Bitcoin, Ethereum, and most other HD (hierarchical-deterministic) crypto wallets to back up and restore a wallet's private keys.

BIP39 phrases turn a block of random binary entropy into a sequence of common English words that are easy to write down and check for typos, and irreversible to guess if even a couple of words are missing. This tool runs the same underlying math wallets use — generation, checksum validation, and PBKDF2 seed derivation — entirely in your browser.

How to use it

To generate a new phrase: choose Generate Mnemonic, pick a word count (12 to 24 words, in steps of 3), optionally set a passphrase, and click Generate. You get a fresh mnemonic, its entropy in hex, and the 512-bit seed derived from it.

To validate or convert an existing phrase: choose Validate / Convert Mnemonic, paste in a space-separated phrase, optionally set the matching passphrase, and click Generate. If every word is in the BIP39 wordlist and the built-in checksum matches, you get the same entropy and seed back — otherwise the tool flags exactly what's wrong (an unknown word or a bad checksum).

What is a BIP39 passphrase?

An optional extra word or phrase (sometimes called the "25th word") that combines with the mnemonic during seed derivation. The same mnemonic with a different passphrase — including no passphrase versus any passphrase at all — produces a completely different, unrelated seed and therefore a different wallet. It is not stored anywhere in the mnemonic itself, so losing it means losing access to funds derived with it, even if the mnemonic is intact.

What is the difference between entropy and the seed?

Entropy is the raw random data the mnemonic encodes — 128 to 256 bits depending on word count — plus a checksum built into the phrase's last word(s). Seed is a fixed 512-bit value derived from the mnemonic (and passphrase) via PBKDF2 with 2,048 rounds; it's the seed, not the entropy, that a wallet actually uses to derive its private keys.

Why does a longer phrase mean more security?

Word count maps directly to entropy: 12 words encode 128 bits, 24 words encode 256 bits. More entropy means more possible phrases and a harder phrase to brute-force — 24 words is the standard choice for high-value wallets, while 12 words is still considered secure for most uses.

Privacy

Everything runs client-side, in your browser — no mnemonic, passphrase, entropy, or seed is ever sent to a server or logged. That said, treat any mnemonic tied to real funds as you would a master password: never enter a phrase you use for actual funds into this or any other website, since anyone who sees the words (or a screen capture, or a browser extension reading the page) can reconstruct the private keys it derives. This tool is intended for learning how BIP39 works and for testing with throwaway phrases, not for handling live wallet secrets.