Generate Secure Random Strings Online Generate cryptographically random strings with customizable character sets.
Random String Generator
Generate cryptographically random strings with customizable character sets.
Set Options
Choose string length, character sets (letters, numbers, symbols), and quantity.
Generate Strings
Click the Generate button to create random strings using your selected settings.
Copy Strings
Copy the generated random strings for your use.
What Is Random String Generator?
A Random String Generator is a tool that creates cryptographically secure random strings using your browser's Web Crypto API, making it suitable for generating passwords, API keys, and other sensitive data. Developers and security professionals use it to create unpredictable text for applications, test data, and session IDs. One specific problem it solves is the need for unique and unguessable identifiers, which can be generated quickly and efficiently.
The tool allows users to customize the output by selecting character sets, including uppercase and lowercase letters, digits, and symbols, as well as specifying the length of the string. For example, a user can choose to generate a random alphanumeric string with a specific length, such as 16 characters, or select multiple character sets to create a more complex password.
What makes this tool different is its ability to generate multiple strings at once, up to 100, and its use of cryptographically secure pseudo-random number generators, ensuring the generated strings are highly unpredictable. It also limits the input length to prevent excessive resource usage, capping it at 10,000 characters. With features like these, users can easily generate random text online, including secure random strings for various applications, making it a reliable choice for developers who need to create test data or other types of random text.
Why Use Random String Generator?
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Cryptographically secure using Web Crypto API
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Customizable character sets and length
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Generate multiple strings at once
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Completely client-side — no server transmission
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Suitable for passwords, tokens, and API keys
Common Use Cases
Password Generation
Create strong, random passwords with mixed character types.
API Keys & Tokens
Generate random strings for API keys, session tokens, and access codes.
Test Data
Create random test data for development and QA testing.
Unique Identifiers
Generate random IDs for databases, files, or temporary resources.
Technical Guide
The generator uses window.crypto.getRandomValues() to fill a Uint32Array with cryptographically random 32-bit integers. Each random value is mapped to a character in the selected character set using modulo arithmetic (value % charsetLength). The Web Crypto API provides cryptographically secure pseudorandom numbers suitable for security-sensitive applications. The modulo operation introduces a negligible bias when the charset length doesn't evenly divide 2^32, but this bias is practically insignificant for strings under 10,000 characters. Multiple strings are generated independently, each with fresh random values.
Tips & Best Practices
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1For passwords, enable all character sets and use at least 16 characters
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2API keys typically use alphanumeric characters (no symbols) at 32-64 characters
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3Symbols increase password strength significantly but may cause issues in some systems
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4Generated strings are cryptographically secure — suitable for security applications
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5Use quantity feature to generate multiple unique strings at once
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📝 Text ToolsFrequently Asked Questions
Q Are the strings truly random?
Q Are the strings stored anywhere?
Q What character sets are available?
Q What's the maximum string length?
Q Can I generate multiple strings at once?
About This Tool
Random String Generator is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.