Should I use a phrase generated here for a real crypto wallet?

No. Treat this as a way to understand or test BIP39 mechanics, not a source of real wallet phrases; a browser tab, however careful, is not the trusted, offline environment real fund recovery phrases need.

How many words does a BIP39 phrase have?

12, 15, 18, 21 or 24 words, corresponding to entropy of 128 through 256 bits in 32-bit steps; this tool exposes that same range via the strength selector.

What does the BIP39 passphrase field actually change?

It's mixed into the PBKDF2 salt when deriving the 512-bit seed from the mnemonic, so the same 12-24 words with a different passphrase produce a completely different seed and, in a real wallet, a different set of addresses.

Why does validation fail on a phrase I typed from memory?

Every BIP39 phrase carries a checksum in its final bits; if any word is wrong, out of order, or not in the standard wordlist, the recomputed checksum won't match and validation reports it as invalid.

BIP39 Mnemonic Generator

Generate and validate BIP39 recovery mnemonics with entropy and seed, locally.

Local, Runs entirely in your browser, your data never leaves your device.

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Generate and validate BIP39 recovery phrases

This tool generates BIP39 mnemonic phrases, the 12-to-24-word recovery phrases used by crypto wallets, using the platform's CSPRNG for entropy and Web Crypto's SHA-256 for the checksum word. It can also validate a phrase you already have and recover its entropy and 512-bit seed (PBKDF2-HMAC-SHA512, 2048 iterations), with an optional passphrase. Everything, including any phrase you paste in, is computed in your browser and never transmitted.

How to use the BIP39 Mnemonic Generator

Pick an entropy strength from 128 to 256 bits, mapping to 12-24 words.
Read off the generated mnemonic, or click regenerate for a new one.
Optionally add a BIP39 passphrase, which changes the derived seed.
Check the entropy (hex) and 512-bit seed shown alongside the phrase.
Switch to validation mode to paste an existing phrase and check its checksum.

A mnemonic's last word encodes a checksum derived from a SHA-256 hash of the entropy, so a single mistyped word will usually fail validation here rather than silently deriving the wrong seed.

This is a generator and inspector, not a wallet. Nothing is stored, and a phrase produced in a browser tab should never be used to hold real funds, generate it on an offline, purpose-built device instead for anything with actual value.

Frequently asked questions

Should I use a phrase generated here for a real crypto wallet?: No. Treat this as a way to understand or test BIP39 mechanics, not a source of real wallet phrases; a browser tab, however careful, is not the trusted, offline environment real fund recovery phrases need.
How many words does a BIP39 phrase have?: 12, 15, 18, 21 or 24 words, corresponding to entropy of 128 through 256 bits in 32-bit steps; this tool exposes that same range via the strength selector.
What does the BIP39 passphrase field actually change?: It's mixed into the PBKDF2 salt when deriving the 512-bit seed from the mnemonic, so the same 12-24 words with a different passphrase produce a completely different seed and, in a real wallet, a different set of addresses.
Why does validation fail on a phrase I typed from memory?: Every BIP39 phrase carries a checksum in its final bits; if any word is wrong, out of order, or not in the standard wordlist, the recomputed checksum won't match and validation reports it as invalid.