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Free Online Cryptographic Random Bytes Generator
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This tool generates cryptographically secure random bytes using your browser's Web Crypto API, with output in Hex, Base64, or Uint8 array format. Truly random bytes are the raw material behind encryption keys, initialization vectors, salts, session tokens, and API secrets — using a weak or predictable random source anywhere in that chain can silently undermine an otherwise strong system, which is why this tool relies on crypto.getRandomValues rather than Math.random. Developers generating AES keys or IVs, engineers seeding salts for password hashing, and anyone who needs guaranteed-unpredictable byte sequences for security-sensitive code will find this useful for quick generation and testing. All randomness is generated and formatted entirely inside your browser — nothing is transmitted to or logged by a server, which matters given that these bytes are often meant to become secret keys. There's no signup and you can choose the exact byte length you need, from a small salt to a full 256-bit key. Pair this with the AES or HMAC tools on this platform if you need to put the generated bytes to immediate use. Scroll down to generate secure random bytes now.
Features
- Uses crypto.getRandomValues for cryptographically secure randomness
- Adjustable output length in bytes (e.g. 16, 32, 64 bytes)
- Multiple output formats: Hex, Base64, and Uint8 array
- Instant client-side generation, no server call
- One-click copy to clipboard
- Suitable for generating keys, IVs, salts, and tokens
- No storage or logging of generated values
- Works fully offline once the page loads
Why use this cryptographic random bytes generator?
- Instant generation with no external dependency
- Fully private — random bytes never leave your browser
- True cryptographic-grade randomness, not pseudo-random
- Flexible output formats fit directly into your code
- Free with unlimited use and no signup
Frequently asked questions
Is this random byte generator cryptographically secure?
Yes, it uses the browser's crypto.getRandomValues API, which draws from the operating system's cryptographically secure random number generator, unlike Math.random which is not suitable for security purposes.
What are random bytes used for?
They're the foundation of encryption keys, initialization vectors (IVs), salts for password hashing, session tokens, and API secrets — anywhere unpredictability is a security requirement.
How many bytes do I need for an AES-256 key?
AES-256 requires exactly 32 bytes (256 bits) of key material; a 16-byte (128-bit) value is typically used for an IV in AES-GCM mode.
Why shouldn't I use Math.random() for security purposes?
Math.random() is a fast, predictable pseudo-random generator designed for simulations and games, not security — its output can potentially be predicted, making it unsafe for keys, tokens, or salts.
What's the difference between Hex and Base64 output?
Hex represents each byte as two readable characters (doubling the length), while Base64 packs data more compactly (about 1.33x the original length), which is often preferred for tokens embedded in URLs or headers.
Are the bytes generated here stored anywhere?
No, generation and display happen entirely in your browser via JavaScript; nothing is transmitted to or retained on a server.
How much entropy is enough for a secure token?
A minimum of 128 bits (16 bytes) of true randomness is generally considered sufficient to make brute-force guessing infeasible for most token use cases.