> bip39 | mnemonic | generator <
// 100% client-side BIP39 seed/recovery phrases — entropy from crypto.getRandomValues(), checksum via Web Crypto SHA-256
// 100% CLIENT-SIDE — your seed phrase is generated locally and never sent over the network
// SECURITY WARNING
Generated locally for development, learning, or testnet use only. For real wallets that secure non-trivial value, ALWAYS use a hardware wallet or trusted offline tool. Never enter a real seed phrase into any web page.
Crypto-Grade Entropy
Random bytes come from window.crypto.getRandomValues(), the same CSPRNG used by Web Crypto, TLS, and modern wallets.
100% Client-Side
The full 2048-word English wordlist is bundled inline. No network calls during generation — you can even disconnect your machine and the tool still works.
12 to 24 Words
Pick any standard BIP39 mnemonic length: 12 (128 bits), 15 (160), 18 (192), 21 (224) or 24 (256). Add an optional passphrase as a 25th-word secret.
// ABOUT BIP39
How Generation Works:
BIP39 turns N bits of entropy into a memorable recovery phrase. We generate ENT bits via crypto.getRandomValues, append ENT/32 checksum bits taken from SHA-256 of the entropy, split the result into 11-bit groups, and map each group to one of 2048 English wordlist entries. With a passphrase, the mnemonic is fed through PBKDF2-HMAC-SHA512 (2048 iterations) to derive the seed.
Example:
12 words = 128 entropy bits + 4 checksum bits = 132 bits = 12 × 11-bit indices into the wordlist.
Standards:
- >BIP-0039: Mnemonic code for generating deterministic keys
- >Official 2048-word English wordlist (11 bits per word)
- >Mnemonic strength: 128, 160, 192, 224, or 256 entropy bits
- >Web Crypto API: crypto.getRandomValues + SubtleCrypto.digest(SHA-256)
Common Use Cases:
- >Bootstrap a new HD wallet (BIP32/BIP44)
- >Test wallet recovery flows in a dev environment
- >Teach key-management concepts to new crypto users
- >Generate disposable seeds for unit tests
- >Audit how mnemonics map to entropy + checksum
>> frequently asked questions
Q: Is it safe to use a generator on a website?
A: For real funds, ALWAYS use a hardware wallet or a trusted offline tool. This generator runs entirely client-side and uses the browser's CSPRNG, but you cannot fully trust any web page with a recovery phrase that secures non-trivial value because malicious extensions or a compromised browser could exfiltrate it. Use it for learning, testing, and development only.
Q: What is a BIP39 passphrase?
A: An optional secret string mixed into PBKDF2 alongside the mnemonic. Different passphrases produce completely different wallets from the same words — useful for plausible deniability or partitioning testnet funds. The trade-off is that if you forget the passphrase the wallet is unrecoverable, even if you still hold the original 12 or 24 words.
Q: 12 vs 24 words — which should I pick?
A: 12 words gives 128 bits of entropy, which is already beyond brute-force at current and foreseeable computing scales. 24 words (256 bits) is preferred for high-value wallets, long-term storage, and post-quantum margin since Grover's algorithm halves effective bits. Bitcoin Core defaults to 24; Trezor and Ledger let you choose.
Q: How is the checksum computed?
A: Take the raw entropy and run it through SHA-256. The first ENT/32 bits of that hash are appended to the entropy. The combined ENT + ENT/32 bits are then split into 11-bit chunks and each chunk indexes the wordlist. This is why a 12-word seed has ENT=128 and 4 checksum bits, while a 24-word seed has ENT=256 and 8 checksum bits.
Q: Can I import this mnemonic into a real wallet?
A: Yes — it follows the standard BIP-0039 English wordlist and the checksum is valid, so any compliant wallet (MetaMask, Trezor, Ledger, Sparrow) will accept it. But again: do not import a phrase generated on a public web page into a wallet that holds real funds. Treat anything from this tool as testnet-only or as an educational artifact.
Q: What does the entropy bits number mean?
A: Entropy is the raw randomness behind the mnemonic, measured in bits. 128 bits means 2^128 possible seeds — a number larger than the count of atoms on Earth. The checksum bits are derived (not random) and exist purely so wallets can detect typos: changing one word almost always invalidates the checksum and produces an error before any funds are sent.