How to Generate a Random String

Quick Answer

A random string is a run of characters with no pattern, used mostly by software: an API key, a session token, a nonce, or a unique name. This tool handles random string generation in your browser, doubling as a token generator, an api key generator, a nonce generator, a general key generator, and a random text generator. Set the length, choose which character sets to allow or type your own alphabet, and copy the result. Each character is a secure random draw, and the tool shows a live entropy estimate so you can size a token correctly. Nothing leaves your device.

Why It Matters

Much of security rests on values that are hard to guess. A session token proves you are logged in. An API key identifies a caller. A password reset link carries a secret that only the right person should have. If any of these follows a pattern, or is too short, an attacker can guess it and take over. Random strings exist to make guessing hopeless.

The trick is that a value is only as safe as its randomness and its length. A token built from a weak random source, or one that is only a few characters long, gives a false sense of security. A generator backed by a cryptographic random source, with a visible entropy estimate, lets you produce values that are genuinely hard to guess and know that they are.

How It Works

You choose an alphabet and a length. The alphabet is the pool of characters the string can contain. You can build it from the standard sets (uppercase, lowercase, numbers, symbols) or type a custom set of exactly the characters you want. The length is how many characters the string will have.

The tool then draws each character from the alphabet using your browser's cryptographic random source. It uses a method that avoids bias, so every character in the pool is equally likely, with no part of the alphabet favored. If you fill in the custom field, it takes priority over the toggles, so the string uses precisely your characters and nothing else.

As you adjust the options, the entropy readout updates. This is how string entropy is measured: entropy is the length multiplied by the base-2 logarithm of the alphabet size, reported in bits. It is the honest measure of guessing difficulty: a 24-character alphanumeric string carries about 143 bits, well past the 128-bit mark that is considered safe for tokens. The strength label turns that number into a word so you can judge at a glance.

Examples

A few settings show the range of what the tool produces. Your own output will differ every time.

• 24 characters, letters and numbers: a general-purpose token with about 143 bits of entropy. Strong enough for API keys and session tokens.
• 32 characters, custom hex alphabet 0123456789abcdef: a 128-bit hex value, the shape many keys and identifiers expect.
• 10 characters, lowercase and numbers: a compact, unique-enough slug or file name, around 51 bits. Fine for naming, not for secrets.
• 40 characters, all sets: a very strong token when a system allows symbols, well over 200 bits.

The pattern is the same as with passwords: length drives strength, and the alphabet sets how much each character is worth. The entropy figure keeps you honest.

Use Cases

Random strings appear throughout software wherever an unguessable or unique value is needed:

• API keys and access tokens for services and integrations.
• Session identifiers and CSRF tokens in web applications.
• Nonces and one-time values that must never repeat.
• Password reset and email verification links.
• Random file names, slugs, and object keys in storage.
• Seed data and fixtures that need many unique strings.

For the security-sensitive cases, size the value with the entropy readout. For naming cases, a shorter string is usually fine.

Advantages

The custom alphabet is the standout feature. Real systems often accept only certain characters, and being able to say exactly which ones the string may contain avoids the frustration of a rejected value. Combined with the length control and the live entropy estimate, it lets you produce a value that fits a specific format and is provably strong.

Doing it locally adds privacy. There is no account, no server that receives your tokens, and no request that could log them. That matters more for random strings than almost anything else, because these values are often the very secrets that protect a system.

Limitations

A random string is only as safe as how it is handled after generation. A strong token pasted into a public chat or committed to a code repository is compromised no matter how much entropy it had. The tool creates the value; protecting it afterward is up to you and your systems.

The entropy figure also assumes the characters are independent and uniform, which they are here, but it cannot account for how a value is used. A perfectly random nonce still fails if it is reused, and a strong key still fails if it is stored in plain text. Treat entropy as a floor on guessing difficulty, not a guarantee of safety.

Privacy

Everything happens on your device. Generating a string makes no network request, logs no analytics event with the value, and never sends it to a server. You can confirm this by opening your browser's developer tools, watching the network tab, and generating a few strings. Nothing goes out.

The tool remembers only your option choices, such as the length and enabled sets, in local storage so the form looks familiar next time. That preference stays on your device and never contains a generated string. Clearing your site data removes it.

Common Mistakes

• Making tokens too short. A handful of characters is easy to guess. Watch the entropy readout and aim for at least 128 bits for secrets.
• Reusing a nonce. A value meant to be used once must be generated fresh each time, or it defeats its purpose.
• Including characters the target rejects. Use the custom field to restrict the alphabet to exactly what the system accepts.
• Storing secrets in plain text. Keep keys and tokens in a secrets manager or an environment variable, not in source code or a note.

Frequently Asked Questions

Short answers to the questions people ask most often, from how long a token should be to how the custom alphabet works, are collected on the tool page itself.

Related Tools

The random string generator sits in the Generators category. For a human-facing secret, the password generator adds an exclude-ambiguous option. For a standard 128-bit identifier in a fixed format, the UUID generator is the right shape.

Where To Go Next

• Random String Generator to create a token or key now.
• Password Generator for a human-facing password.
• UUID Generator for a standard unique identifier.
• Generators to browse every generator on the site.