`crypto.randomBytes()`

Generates cryptographically strong pseudo-random bytes.

Since Node 0.5 Spec ↗

Syntax

crypto.randomBytes(size[, callback])

Parameters

Name	Type	Required	Description
`size`	`number`	Yes	The number of bytes to generate.
`callback`	`function`	No	Optional `(err, buf)` callback for async generation.

Returns

Buffer — A Buffer of random bytes (sync form).

Examples

import { randomBytes } from 'node:crypto';

const token = randomBytes(32).toString('hex');
console.log(token.length);

Output

import { randomBytes } from 'node:crypto';

const session = randomBytes(24).toString('base64url');
console.log(session);

Output

kR3p-9fL2xQ7vN1mZ8aB4cD6

Notes

Use for session tokens, password reset codes, and salts; never use `Math.random()` for security. Generating large amounts synchronously blocks the event loop; pass a callback (or use `randomFill`) for big sizes.