BIP39 in 180 Lines of Vanilla JS — Mnemonic Generation, Validation, Seed Derivation, and the Japanese Wordlist Trap

The 12-to-24 word "seed phrase" inside every hardware wallet and software wallet is BIP39 . The spec is short — one file. Implement it from scratch and you discover that the only place where independent implementations actually disagree is the Japanese wordlist edge case, which catches even seasoned crypto libraries. Here's a zero-dependency, SubtleCrypto -only, 180-line BIP39 implementation, verified against both the Trezor and bip32JP test vectors. 🔐 Demo : https://sen.ltd/portfolio/bip39-too