What is a random string generator?

A random string generator creates sequences of characters chosen randomly from a defined character set. It is used for generating passwords, tokens, salts, and unique identifiers.

What is entropy in random strings?

Entropy measures the unpredictability of a random string. It is calculated as length × log₂(charset size). Higher entropy means stronger resistance to brute-force attacks.

A Cryptographically Secure Pseudo-Random Number Generator (CSPRNG) produces random numbers suitable for cryptographic operations. It uses unpredictable sources of entropy from the operating system.

What are random strings used for in security?

They are used for generating session tokens, API keys, CSRF tokens, password reset links, encryption keys, salts for password hashing, and one-time passwords (OTPs).

/ /Random String Generator

Random String Generator

Generate cryptographically secure random strings for passwords, tokens, API keys, and unique identifiers.

Inputs

Length (16)

Uppercase (A-Z) Lowercase (a-z) Numbers (0-9) Special Characters Exclude Ambiguous (0OIl1)

Count (1)

Results

Click "Generate" to create random strings.

Related Tools

References

Frequently Asked Questions

What is a random string generator?: A random string generator creates sequences of characters chosen randomly from a defined character set. It is used for generating passwords, tokens, salts, and unique identifiers.
What is entropy in random strings?: Entropy measures the unpredictability of a random string. It is calculated as length × log₂(charset size). Higher entropy means stronger resistance to brute-force attacks.
What is a CSPRNG?: A Cryptographically Secure Pseudo-Random Number Generator (CSPRNG) produces random numbers suitable for cryptographic operations. It uses unpredictable sources of entropy from the operating system.
What are random strings used for in security?: They are used for generating session tokens, API keys, CSRF tokens, password reset links, encryption keys, salts for password hashing, and one-time passwords (OTPs).
Why should I exclude ambiguous characters?: Ambiguous characters like 0/O, 1/l/I can be confused with each other, especially in printed or handwritten contexts. Excluding them reduces readability errors.
What is a salt in password hashing?: A salt is a random string added to a password before hashing to ensure that identical passwords produce different hashes. This prevents rainbow table attacks.
What makes a good API key?: A good API key is long (at least 32 characters), uses a large character set (uppercase, lowercase, digits), and is generated using a cryptographically secure random generator.
How long should a random token be?: For security tokens, at least 128 bits of entropy is recommended. With a 62-character set (a-z, A-Z, 0-9), this requires about 22 characters. For high-security applications, 256 bits (43 characters) is better.
What is the difference between random and unique?: Random means each character is chosen independently. Unique means a value has not been seen before. Random strings can collide by chance; adding uniqueness guarantees distinctness.
Can random strings be predicted?: If generated using a weak PRNG like Math.random(), they can be predicted. Always use cryptographically secure methods (CSPRNG) for security-sensitive applications.
What encoding is used for random strings?: Common encodings include alphanumeric (base62), hexadecimal (base16), base64, or custom character sets. Base64 is compact but includes + and / characters that may need URL encoding.
What is a UUID vs a random string?: UUIDs are 128-bit identifiers with a specific structure (8-4-4-4-12 hex digits). Random strings can have any length and character set. UUIDs guarantee uniqueness without a central authority.
How are random strings generated in browsers?: Modern browsers provide crypto.getRandomValues() which uses a CSPRNG. This should be used instead of Math.random() for any security-related random string generation.
What are the best practices for generating passwords?: Use at least 12-16 characters, include uppercase, lowercase, digits, and special characters. Avoid dictionary words, patterns, and personal information. Use a password manager to generate and store them.