Cereio

Random String Generator

Settings
Presets
Basic Settings
Length
Quantity
Character Types
Uppercase (A-Z)
Lowercase (a-z)
Numbers (0-9)
Symbols (!@#$%...)
Character pool: 62 · Estimated entropy: 71 bits
Generated String
Click "Generate String" to create random strings

About Random String Generator

Create cryptographically secure random text for API keys, tokens, test data, hexadecimal IDs, URL-safe identifiers, and numeric codes. Start from a preset or provide your own character set.

Key Features

Useful Lengths

Choose a length from 8 to 64 characters.

Character Options

Choose built-in character groups or enter a custom character set.

Bulk Generation

Generate multiple random strings at once.

Secure Randomness

Uses the browser Web Crypto API instead of Math.random().

Copy Support

One-click copy for any generated string.

Clearer Codes

Optionally exclude 0/O and 1/l/I to reduce typing mistakes.

Useful Presets

Start with API token, hexadecimal ID, URL-safe, or numeric-code settings.

How to Use

  1. 1Set the desired string length.
  2. 2Choose a preset, character types, or a custom character set.
  3. 3Select how many strings to generate.
  4. 4Click 'Generate' and copy the results.

Pro Tips

  • 💡For API keys, use at least 32 characters with mixed types.
  • 💡Exclude ambiguous characters (0/O, 1/l) for user-facing codes.
  • 💡Use only alphanumeric for URL-safe strings.
  • 💡For test data, generate strings that match your expected input patterns.

Common Examples

URL-safe identifier

Input
Length 16 · uppercase + lowercase + numbers
Output
aZ8mQ2vL7nK4xP9c

Letters and numbers avoid escaping when the value is used in a URL.

Long API token

Input
Length 32 · all character groups
Output
G7@vL2#pQ9!xR4$mT8&kN6*zC3%wF5_h

Use a long mixed string for generated secrets, and store it in a secret manager.

Hexadecimal identifier

Input
Hex ID preset · length 32
Output
7f3a91c204d84e6bb51672ef8a09cd31

The preset limits output to lowercase hexadecimal characters for test IDs and fixtures.

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Create hashes from text without uploading it.

Frequently Asked Questions

Are the strings truly random?
The browser's Web Crypto API produces cryptographically strong pseudorandom values. This is appropriate for generated tokens and avoids the predictable output of Math.random().
Can I exclude confusing characters?
Yes. Enable 'Exclude similar characters' to remove 0, O, 1, lowercase l, and uppercase I.
Can I use my own character set?
Yes. Open Advanced Options and enter the exact characters you want. Duplicate characters are removed so every distinct character has the same selection probability.
How long should my API key be?
For security-sensitive applications, use at least 32 characters. 64 characters provides excellent security with mixed character types.
Is the generation secure?
Yes, all generation happens locally in your browser using secure random APIs. No data is sent to any server.