Lab — Web3 tool
Seed Phrase Lab is a free online tool that generates BIP39 recovery phrases from real cryptographic entropy and validates any phrase against the official 2048-word list and its checksum — entirely in your browser, so you can learn how wallets work without risking anything.
Never use a phrase generated here for real funds. A recovery phrase is the wallet — anyone who sees it can take everything. Never share a phrase with anyone, never type one into a website that asks for it, and never store one in a screenshot, email or cloud note. Nothing on this page is sent or saved anywhere.
Generate a phrase
Pick a length and press Generate — the words appear here, numbered in order.
Validate a phrase
Validation checks the word count, that every word is in the official BIP39 list, and that the checksum matches.
A wallet starts with random entropy — 128 bits for a 12-word phrase, 256 bits for 24 words. It hashes that entropy with SHA-256 and takes the first few bits of the hash as a checksum (4 bits for 128-bit entropy, 8 for 256-bit). Entropy + checksum is then split into 11-bit groups, and each group is an index (0–2047) into the official BIP39 wordlist of 2048 English words. That is the whole trick: the words are just a human-readable encoding of random bits plus a checksum.
The checksum is why a wallet can tell you a phrase is wrong. Change one letter, swap two words, or mistype a word and the checksum almost certainly no longer matches — so the wallet refuses the phrase instead of silently opening the wrong wallet. Validating a phrase never needs the internet: the wordlist and the SHA-256 check are all that is required, which is why this page works entirely offline.
The test-vector phrase — abandon eleven times followed by about — is the official BIP39 example for all-zero 128-bit entropy. It is a public test case, not a real wallet: never use it, or any phrase from this page, with real funds.