BIP39 Mnemonic Generator
Generate a random BIP39 recovery phrase of 12 to 24 words in several languages, or convert an existing mnemonic back into its raw entropy, entirely in your browser.
BIP39 Mnemonic Generator — Create a cryptographically random BIP39 mnemonic seed phrase for a crypto wallet, choosing 12, 15, 18, 21, or 24 words and one of several wordlist languages, then copy it with one click. You can also switch to the reverse mode and paste an existing phrase to validate it and recover the raw entropy bytes behind it. Everything runs locally with the audited @scure/bip39 library, so your seed phrase is generated and checked in the browser and never touches a server.
What is BIP39 Mnemonic Generator?
The BIP39 Mnemonic Generator is a free, in-browser tool for working with the recovery phrases (also called seed phrases or mnemonics) defined by Bitcoin Improvement Proposal 39. Crypto users, wallet developers, and QA engineers use it to mint a fresh random phrase for a new test wallet, to see how word count maps to entropy strength, or to verify and decode a phrase they already have. In the Generate direction you pick a word count and language and press Generate to mint a phrase whose words and checksum come straight from the BIP39 wordlist; the Stat readouts show the resulting word count and the entropy strength in bits. In the Decode direction you paste a mnemonic and the tool validates its checksum against the selected language wordlist and prints the underlying entropy as a hexadecimal string. The randomness comes from the browser's cryptographically secure generator, and validation and conversion follow the BIP39 specification exactly.
How to use BIP39 Mnemonic Generator
- Choose a direction with the segmented control: Entropy to mnemonic to create a phrase, or Mnemonic to entropy to decode one.
- Open Settings to pick the word count (12, 15, 18, 21, or 24) and the wordlist language.
- In generate mode, press Generate to mint a fresh random recovery phrase; press it again any time for a new one.
- Read the phrase from the output block and check the word count and entropy strength shown in the stats.
- In decode mode, paste an existing mnemonic; the matching entropy appears automatically in hexadecimal once the checksum validates.
- Use the copy button next to the phrase or the entropy to put the result on your clipboard.
Examples
Minting a 12-word English phrase
Keep the word count at 12 and the language at English, then press Generate. A twelve-word phrase appears in the output, the Words stat reads 12, and the Strength stat reads 128 bits.
A stronger 24-word phrase
Switch the word count to 24 in Settings and press Generate. The phrase now has twenty-four words and the Strength stat reads 256 bits, the maximum BIP39 entropy.
Decoding a known test vector
Input
legal winner thank year wave sausage worth useful legal winner thank yellow
Output
7f7f7f7f7f7f7f7f7f7f7f7f7f7f7f7f
Frequently asked questions
- Is my seed phrase sent anywhere?
- No. The phrase is generated, validated, and decoded entirely in your browser with the @scure/bip39 library. Nothing is uploaded to or stored on any server, so the tool works offline and your seed phrase never leaves the page.
- Should I use a phrase from here to hold real funds?
- It is best treated as a learning, testing, and development tool. For real funds, generate your seed on a dedicated hardware wallet or trusted offline device; any phrase typed into or generated in a web browser should be considered exposed to that environment.
- What does the word count change?
- More words means more entropy: 12 words is 128 bits, 15 is 160, 18 is 192, 21 is 224, and 24 is 256 bits. The Strength stat shows the value for your current selection.
- Which languages are supported?
- English, Japanese, Korean, Spanish, and Simplified Chinese BIP39 wordlists. The chosen wordlist is loaded on demand, and decoding must use the same language the phrase was created in.
- Why is my pasted phrase reported as invalid?
- BIP39 phrases carry a checksum, so a misspelled word, a word missing or out of order, the wrong word count, or the wrong language selected will all fail validation. Check that every word comes from the selected language wordlist and that the count is 12, 15, 18, 21, or 24.
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