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Cryptography

BIP39 seed phrase generator

BIP39 Mnemonic draws 12 or 24 words from the official 2048-word BIP-0039 list, folding a checksum into the final word so every phrase it generates validates in any standard wallet. A 12-word phrase encodes 128 bits of entropy, a 24-word phrase 256 bits, and the "Words" list switches between the two lengths. Developers use such phrases to test wallet flows and seed local nodes without touching real funds.

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How to use BIP39 Mnemonic

  1. Open BIP39 Mnemonic in the Toolbox101 app; a random 12-word phrase appears in the Output box straight away.
  2. Pick 12 words or 24 words in the Words list and the tool draws a matching phrase. Generate New draws another whenever you need one.
  3. Optionally type a Passphrase to see the 512-bit seed that wallets derive from the phrase and that passphrase.
  4. Read the phrase in the Output box; the last word carries the checksum that makes the whole phrase valid in BIP39 wallets.
  5. Click Copy, store the phrase offline, and clear it from your clipboard before moving on.

Worked example

BIP39 Mnemonic gives a different result every time, so yours will differ. This is one run:

Output

slice chronic wall scheme sound among cute loop laptop family route course

Frequently asked questions

Is it safe to generate a wallet seed phrase online?

A seed phrase is the wallet, so the page is not the main risk. The machine is. Nothing generated here is uploaded, but browsers keep history, extensions can read the clipboard, and screenshots linger. For balances that matter, generate the phrase on an offline or air-gapped device you control, and keep this tool for testnets and throwaway wallets.

What exactly is a BIP39 mnemonic?

A BIP39 mnemonic is the BIP-0039 way to represent wallet entropy as words. Random bits are split into 11-bit groups and mapped to a fixed 2048-word list, then the leading bits of a SHA-256 digest are folded in as a checksum so software can reject a mistyped phrase. Wallets derive keys from the phrase deterministically.

Can I reproduce the phrase shown in the example?

No. Every run draws fresh random entropy, so the tool never repeats a phrase. The example is one real run with a valid checksum, and because it is published here it must never hold funds.

What is the difference between 12 and 24 words?

A 12-word phrase encodes 128 bits of entropy and a 24-word phrase 256 bits. Both are standard, both validate, and both give the same per-word security against guessing. Twenty-four words leaves more margin if part of the phrase is ever lost or compromised, which is why hardware wallets often default to it.

Can I import a generated phrase into a real wallet?

Yes: any BIP39-compliant wallet derives the same keys from the same phrase, which is exactly why a phrase published anywhere must never hold funds. Import into testnet wallets only, and treat the phrase as the wallet itself.

What does the optional passphrase do?

A BIP39 passphrase, sometimes called the 25th word, is mixed into the seed together with the phrase. A different passphrase gives a completely different wallet, and there is no way to tell a wrong one from a right one, so losing it loses the funds. When you type one, the tool also prints the 512-bit seed (PBKDF2-HMAC-SHA512, 2,048 rounds) that wallets derive their keys from.

Use BIP39 Mnemonic now

Open BIP39 Mnemonic in the app

Runs in your browser. Nothing you type is uploaded.