Random Byte/Hex Generator Online | Secure CSPRNG (Hex, Base64, Binary)

This tool generates raw random material from the Web Crypto API's cryptographically secure random number generator (CSPRNG). Every value is drawn fresh from the operating system entropy pool — nothing is derived from a seed, and nothing leaves your browser. Specify 1 to 1024 bytes, choose up to four output formats simultaneously (Hex, Base64, URL-safe Base64, and binary), and generate up to 100 values in a single batch. The tool works fully offline once the page is cached.

Byte Length Recommendations

Bytes	Bits	Hex Length	Best for
12	96	24 chars	AES-GCM nonces (IVs)
16	128	32 chars	Session tokens, minimum security
32	256	64 chars	API keys, AES-256 keys, shared secrets
64	512	128 chars	Long-lived master secrets

Code Examples

Generate random bytes with Web Crypto API:

// Browser — Generate 32 random bytes
const bytes = new Uint8Array(32);
crypto.getRandomValues(bytes);

// Convert to hex
const hex = Array.from(bytes)
  .map(b => b.toString(16).padStart(2, '0'))
  .join('');
console.log(hex);  // 64 hex characters

// Convert to Base64
const base64 = btoa(String.fromCharCode(...bytes));
console.log(base64);  // 44 characters

// URL-safe Base64
const urlSafe = base64.replace(/+/g, '-').replace(///g, '_').replace(/=+$/, '');
console.log(urlSafe);

# Python — Generate random bytes
import secrets
import base64

# 32 random bytes
random_bytes = secrets.token_bytes(32)

# Hex output
print(random_bytes.hex())

# Base64 output
print(base64.b64encode(random_bytes).decode())

# URL-safe Base64
print(base64.urlsafe_b64encode(random_bytes).decode().rstrip('='))

Security Notes

• Use CSPRNG for security — this tool uses crypto.getRandomValues() (CSPRNG); never use Math.random() for cryptographic purposes.
• Entropy equals byte length × 8 — 32 bytes provides 256 bits of entropy, matching AES-256 security level.
• Base64URL for web tokens — use URL-safe Base64 for API keys and tokens to avoid encoding issues in URLs.
• Fresh on each click — every generation draws new random bytes; previous values cannot be predicted.

Related Tools

Need human-readable secrets? Try the Passphrase Generator. For password creation, see the Password Generator. To validate BIP39 mnemonics generated from random entropy, use the BIP39 Mnemonic Validator.