BIP39 Mnemonic Passphrase Generator — Free
Runs 100% in your browser — your files never leave your device.
BIP39 mnemonics turn cryptographic entropy into memorable word lists for wallets and seeds. Generate fresh entropy, get the matching 12-to-24-word phrase, and convert in both directions — paste a mnemonic to recover its entropy. Ten wordlists ship, from English to Japanese, all computed locally.
How it works
- 1
Generate entropy
Fresh random entropy is drawn from your browser on load.
- 2
Pick a language
Ten BIP39 wordlists are available, including English, Spanish, and Japanese.
- 3
Read or paste a mnemonic
Copy the phrase, or paste one to see and validate its entropy.
About this tool
What BIP39 is
BIP39 is the cryptocurrency standard for representing random keys as word sequences: 2048 carefully chosen words where each encodes 11 bits. Twelve words carry 128 bits of entropy; twenty-four carry 256. The wordlist is chosen so every word is distinguishable from its first four letters.
Entropy is the entire security
The words are not a password you invent — they are a precise encoding of random bits, and the bit count IS the security. Twelve words is considered strong for most wallets; twenty-four is the maximum. Never accept fewer, never type a seed phrase generated anywhere but a trusted local source.
Handle the output with care
Anyone with these words owns everything they protect — no reset, no support. Write them on paper, store them offline, and never photograph, cloud-sync, or paste them into a website. This tool generates them locally; the words exist nowhere else but your screen.
Frequently asked questions
Can I use these words as a regular passphrase?
You can — the wordlist makes memorable high-entropy passphrases. Note that BIP39 words used as ordinary passphrases carry the same entropy as their bit count suggests.
Why 12 words instead of a password?
128 bits of true randomness is stronger than nearly every human-chosen password, and the word sequence is transcribable by hand — the combination of strength and writability is the design.
Does the generator keep my words?
No — generation happens in your browser from local randomness, and nothing persists. Copy the words and store them offline immediately.