Random Code & String Generator

What Is a Random Code Generator?

A random code generator creates batches of random strings using a specified character set and length. These codes are useful for coupon codes, referral codes, one-time passwords (OTPs), unique identifiers, test data, raffle entries, serial numbers, voucher codes, and more.

This tool runs entirely in your browser using the Web Crypto API (crypto.getRandomValues()), which provides cryptographically secure randomness. No data is sent to any server.

How to Use This Tool

1. Set the number of strings you need (1–100).
2. Set the length of each string (1–32 characters).
3. Choose your character sets — numeric digits (0–9), uppercase letters (A–Z), lowercase letters (a–z), or any combination.
4. Toggle uniqueness — enable this if you need every string in the batch to be different (no duplicates).
5. Click "Generate Strings" and copy the results.

Common Use Cases

How the Randomness Works

Unlike Math.random(), which uses a pseudo-random number generator (PRNG) that can be predicted if the seed is known, this tool uses the browser's Web Crypto API. The crypto.getRandomValues() method draws entropy from the operating system's cryptographic random number generator, making the output suitable for security-sensitive applications.

The uniqueness check, when enabled, uses an in-memory Set to track generated strings and re-rolls any duplicates. For very large pools (e.g., 62 characters at length 8 = 218 trillion combinations), collisions are astronomically rare. For small pools (e.g., 10 digits at length 3 = 1,000 combinations), collisions become more likely, and the tool will warn you if it cannot produce enough unique results.

Best Practices

• Use longer strings for security. An 8-character alphanumeric code (62-char pool) has 218 trillion possibilities. A 4-character code has only 14 million — easily brute-forced.
• Avoid ambiguous characters in printed codes. If your codes will be typed manually, consider using only uppercase + digits (no lowercase) to avoid confusion between O/0, l/1/I, etc.
• Always enable uniqueness for coupon codes. Duplicate coupon codes can lead to double-redemption issues and revenue loss.
• Use numeric-only for OTPs and PINs. Numeric codes are easier to enter on phone keypads and are the industry standard for SMS verification.
• Don't use these for cryptographic keys. While the randomness source is cryptographically secure, proper key generation requires additional considerations like key derivation functions and secure storage.

Common Mistakes to Avoid

• Too-short codes for public use. A 4-digit code has only 10,000 possible values. If exposed publicly (e.g., promo codes on social media), they can be guessed within seconds.
• Not checking for uniqueness. If you generate 100 codes from a small pool without uniqueness enabled, you may get duplicates.
• Using sequential or patterned codes. Codes like PROMO001, PROMO002 are predictable. Random codes prevent users from guessing valid codes.
• Reusing codes across campaigns. Always generate fresh codes for each campaign to avoid tracking and redemption issues.

Frequently Asked Questions