Enter a password and salt, pick the hash and iteration count, and PBKDF2 derives a hex key locally using the Web Crypto API.
Password-Based Key Derivation Function 2 stretches a password with many HMAC iterations and a salt to produce a strong cryptographic key.
More iterations slow down each guess, making brute-force attacks against the derived key far more expensive.
A unique random salt per password. It prevents rainbow-table attacks and should be stored alongside the derived key.