BIP39 Mnemonic Generator & Validator | Seed Phrase Checker & Multi-Chain Wallet

This tool generates and validates BIP39 mnemonic phrases (12, 15, 18, 21, or 24 words) and derives BIP32/BIP44 wallet addresses for 18 cryptocurrencies via SLIP-0010. After validation, the mnemonic is fed into PBKDF2-HMAC-SHA512 with 2048 iterations to produce a 512-bit seed; an optional passphrase — the so-called "25th word" — modifies the salt so the same mnemonic with different passphrases yields completely independent wallets. Bitcoin derivation covers all four address formats (Legacy 1…, SegWit 3…, Native SegWit bc1q…, Taproot bc1p…), and EVM chains (ETH, BSC, Polygon, Avalanche) share the 0x address space. All computation uses the Web Crypto API and verified cryptographic libraries — nothing leaves your browser.

BIP39 Word Count & Entropy

Words	Entropy (bits)	Checksum (bits)	Total (bits)	Use case
12	128	4	132	Standard wallet (most common)
15	160	5	165	Medium security
18	192	6	198	High security
21	224	7	231	Very high security
24	256	8	264	Maximum security (hardware wallets)

Bitcoin Address Derivation Paths

Format	Prefix	BIP44 Path	Recommendation
Legacy	1...	m/44'/0'/0'/0/0	Legacy compatibility only
SegWit	3...	m/49'/0'/0'/0/0	Good, but Native SegWit better
Native SegWit	bc1q...	m/84'/0'/0'/0/0	★ Recommended (lower fees)
Taproot	bc1p...	m/86'/0'/0'/0/0	★ Newest, best privacy

Code Examples

// Browser — BIP39 seed derivation (PBKDF2-HMAC-SHA512)
const mnemonic = 'abandon abandon ... about';  // 12 words
const passphrase = '';  // optional "25th word"
const encoder = new TextEncoder();
const password = encoder.encode(mnemonic.normalize('NFKD'));
const salt = encoder.encode(('mnemonic' + passphrase).normalize('NFKD'));
const key = await crypto.subtle.importKey(
  'raw', password, 'PBKDF2', false, ['deriveBits']
);
const seed = await crypto.subtle.deriveBits(
  { name: 'PBKDF2', salt, iterations: 2048, hash: 'SHA-512' },
  key, 512
);
console.log(Array.from(new Uint8Array(seed))
  .map(b => b.toString(16).padStart(2, '0')).join(''));  // 64-byte hex

# Python — Mnemonic validation (checksum check)
import hashlib
words = 'abandon abandon ... about'.split()
idx = [wordlist.index(w) for w in words]
bits = ''.join(bin(i)[2:].zfill(11) for i in idx)
entropy_bits = bits[:128]  # for 12 words
checksum_bits = bits[128:]  # last 4 bits
expected = hashlib.sha256(bytes.fromhex(
    hex(int(entropy_bits, 2))[2:].zfill(32)
)).digest()[0] >> 4
assert checksum_bits == bin(expected)[2:].zfill(4)
print('Checksum valid')

Security Notes

• Never enter real mnemonics online — This tool runs 100% client-side, but as a rule: real wallet mnemonics should only be entered on air-gapped hardware wallets or offline tools.
• Passphrase is a second factor — The same mnemonic with different passphrases produces completely different seeds. Losing the passphrase means losing access to the wallet.
• xprv = master key — The extended private key (xprv) can derive all child private keys. Treat it with the same secrecy as the mnemonic itself.
• Checksum catches typos — BIP39 includes a checksum in the last few bits. If you mistype a word, validation fails immediately — the checksum is your first line of defense against backup errors.

Related Tools

Need to generate the random entropy for a custom mnemonic? Use the Random Byte Generator. For human-readable secrets instead of raw bytes, try the Passphrase Generator. To check the strength of your passphrase, see the Entropy Calculator.