BIP39 mnemonic generator
Generate 12/15/18/21/24-word BIP39 mnemonics, turn entropy back into a phrase, derive entropy or a seed (PBKDF2-SHA512, 2048 rounds) and validate phrases — all locally in your browser.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Generate a mnemonic
Entropy comes from the browser crypto.getRandomValues; the phrase never leaves this page.
Click “Generate” for a fresh BIP39 mnemonic
Parse & validate
Restore mnemonic from entropy
What this tool does
- Generate a 12/15/18/21/24-word BIP39 mnemonic for a self-hosted wallet, a test environment or a demo — entropy comes from the browser crypto.getRandomValues.
- Validate a mnemonic someone handed you: check the word count, whether every word is in the English wordlist, and whether the checksum passes, all in one pass.
- Restore a mnemonic from hex entropy, or turn a mnemonic back into entropy, and compare the two directions.
- Derive the 64-byte BIP39 seed (PBKDF2-HMAC-SHA512, 2048 rounds) with an optional passphrase to cross-check what another wallet produces.
Example
Input
00000000000000000000000000000000
Output
abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about
This is the standard BIP39 test vector: 16 bytes of zero entropy maps to 12 words, and the final word about carries the checksum. It only demonstrates the entropy-to-mnemonic mapping — never use all-zero entropy for real funds.
Frequently asked questions
Is the generated mnemonic really random?
The entropy comes from the browser crypto.getRandomValues, which is the OS-provided cryptographically secure source, not Math.random. It still runs inside a browser though: on a compromised machine or with a malicious extension even a good RNG cannot save you, so real funds belong in a hardware wallet.
What is the checksum for?
BIP39 appends SHA-256 check bits to the entropy and then maps 11-bit groups onto words. Having every word in the wordlist is therefore not enough — the check bits inside the last word must match. Shuffling or editing words usually breaks the checksum and you get “wrong word count or checksum”.
How does the passphrase relate to the mnemonic?
The passphrase is BIP39’s optional extra, sometimes called the 25th word. The seed comes from PBKDF2-HMAC-SHA512 run over the mnemonic with the salt “mnemonic” + passphrase for 2048 rounds, so the same phrase with a different passphrase produces a completely different wallet. Forget the passphrase and the funds are gone — there is no recovery path.
Is it safe to paste a real mnemonic here?
No. This tool runs entirely locally and uploads nothing, but you cannot verify that the environment is trustworthy — a shared computer, an injected browser, a screenshot or clipboard sync can all leak the phrase, and a leaked phrase means irreversible loss. Treat this as a learning and verification tool only; never paste a real mnemonic into a web page on any networked device.
Does it support Chinese or other wordlists?
Only the BIP39 English wordlist (2048 words). A mnemonic in another language is reported as containing words that are not in the English wordlist. The English list has the best wallet interoperability and is the default almost everywhere.
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