BIP39 passphrase generator

THE PRACTICAL GUIDE · NORMANDIN SYSTEMS

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The BIP39 generator converts hexadecimal entropy into a mnemonic word sequence and converts a compatible mnemonic back into entropy. Choose a word-list language, enter a demonstration value in Entropy seed, or edit the Passphrase mnemonic field to inspect the reverse representation. The refresh control generates new entropy, and the copy controls copy the corresponding text. Although the interface calls the words a passphrase, they are a BIP39 mnemonic; the optional extra passphrase used by some wallet seed-derivation workflows is a different input and is not offered here. This page is useful for studying word lists and test vectors. Never use the public example below to protect assets or accounts.

Guide updated October 13, 2026

How to use this tool

1. Select the language of the mnemonic word list before entering or interpreting a phrase.
2. For a reproducible test, enter 00000000000000000000000000000000 in the Entropy seed field and choose English.
3. Inspect the generated mnemonic. To test the reverse direction, enter a compatible mnemonic into the mnemonic field and inspect the recovered entropy.
4. Use refresh to generate a new entropy value when testing generation. Copy the representation you need and verify compatibility with the intended receiving implementation.

SEE IT IN PRACTICE

A worked example

English word list; entropy 00000000000000000000000000000000

abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about

Sixteen zero bytes provide 128 bits of demonstration entropy. The final word incorporates checksum information. This predictable, public vector is suitable for a test and unsafe for a real wallet.

How the checksum becomes part of the words

BIP39 appends checksum bits to entropy and divides the resulting bits into eleven-bit groups. Each group selects one word from a 2,048-entry list. For the 128-bit example, four checksum bits make 132 bits, yielding twelve words. That relationship explains why an arbitrary collection of valid words is not necessarily a valid mnemonic. A changed word can alter both the recovered entropy and whether the checksum agrees; the visible meaning of the words is irrelevant to the mapping.

Distinguish entropy conversion from wallet recovery

The two editable representations on this page are linked: entering valid entropy produces words, and entering compatible words produces entropy. There are no account balances, derivation paths, addresses, or wallet-connection controls in this operation. Standard BIP39 defines several entropy sizes, but the page's own input validation can restrict what it accepts; use an accepted test vector when checking this implementation. A successful conversion is a format check, not evidence that newly generated material has been securely backed up or that a particular wallet will derive the account you expect.

When this tool is useful

• Learn how entropy and checksum bits become mnemonic words.
• Compare a known BIP39 test vector with a receiving library.
• Explore why mnemonic language and word order must be preserved.

Tips for a better result

• Preserve the exact word order and spelling. Replacing a word with a synonym changes the encoded data.
• Use disposable phrases when testing or sharing screenshots; a real recovery phrase is sensitive access material.
• Read validation messages carefully. This interface does not expose every parameter involved in wallet seed derivation or address generation.

Frequently asked questions