Random Hex Generator (Bytes, Keys, Numbers)

Random hex strings are everywhere in development: encryption keys and IVs, salts, session secrets, test data, colour seeds and unique tokens. This generator draws bytes from the browser’s cryptographically secure random source and formats them the way you need — plain hex, 0x-prefixed, spaced or colon-separated bytes, a C or JavaScript byte array, or \x escapes — and can also pick uniformly random hex numbers between two bounds of any size.

How to use this tool

1. Choose random bytes or random numbers in a range.
2. Set the number of bytes per value (16 for a 128-bit key, 32 for 256-bit) or the hex range.
3. Pick the output format, case and how many values.
4. Copy the values; the first is also shown as Base64.

Formula

entropy = bytes × 8 bits range values: uniform integer in [min, max] by rejection sampling

For a range, enough random bits to cover max − min are drawn; results outside the range are thrown away and redrawn, so every value is exactly equally likely (taking the remainder would favour small values). Big ranges use BigInt, so 256-bit bounds work.

Example

16 random bytes give a 32-digit hex string such as 3fa94c…e1, carrying 128 bits of entropy — the size of an AES-128 key. As a C array the same 4 bytes 3f a9 4c 07 become { 0x3f, 0xa9, 0x4c, 0x07 }, 26 characters long.