Random String Generator

Randomly generated strings are used for API keys, session tokens, one-time codes, nonces, test data, and unique filenames. The security of a random string for authentication purposes depends on two factors: the size of the character set it is drawn from and its length, which together determine its entropy — the number of bits of unpredictability.

Cryptographic randomness is essential for security-critical tokens. A token generated with a cryptographically secure pseudo-random number generator (CSPRNG) cannot be predicted even if an attacker knows many previous values. This tool uses the browser's crypto.getRandomValues() API, which provides cryptographically strong randomness. Do not use Math.random() for security tokens — it is not cryptographically secure.

Entropy determines how resistant a token is to brute-force guessing. A token of length n drawn from an alphabet of k characters has log2(k^n) bits of entropy. For session tokens, 128 bits of entropy is commonly recommended (22 characters in Base64). For API keys, 256 bits provides a very large safety margin. A 32-character alphanumeric string (lowercase + uppercase + digits, 62 characters) has about 190 bits of entropy — sufficient for virtually any application.