Random String Generator
Generate cryptographically secure random strings, passwords, API keys, and tokens with customizable length and character sets.
Why Use Random String Generator?
Most random string generators on the web use Math.random() under the hood, which is dangerously weak — Mozilla and the V8 team explicitly warn against using it for security-relevant values. This tool uses crypto.getRandomValues() (the same RNG your browser uses for TLS), shows you the entropy in bits and the rough brute-force time, and lets you exclude ambiguous characters when a human will need to type the value. If you're rotating an API key, generating a one-off password for a teammate, or pre-seeding test data, you want a tool that produces secure output by default — not one that proudly says 'powered by Math.random()' in its README.
How to Use Random String Generator
- Choose a length between 1 and 256 characters using the slider or input.
- Toggle the character sets you want to include: lowercase, uppercase, numbers, and symbols. Optionally add a custom character set or exclude ambiguous characters (0/O, 1/l/I).
- Click a preset (Password, API Key, Hex String, Token, Variable Name) to apply common configurations in one click.
- Click Generate to create a single string, or switch to Bulk mode to generate up to 100 strings at once and download as a .txt file.
- Copy individual strings or the whole batch to your clipboard with one click.
Worked Examples
32-char alphanumeric API key
Length 32, lowercase + uppercase + numbers, no symbols
K9pXmA2vBnQ7tZ4yU8wJsR3hL6cD0fNg
≈190 bits of entropy — safe for production API keys.
16-char strong password
Length 16, all character sets including symbols
p3$Vk!8mTn@2qXz#
≈105 bits of entropy — strong enough that brute-forcing it is computationally infeasible.
Bulk generate 50 invite tokens
Bulk mode, length 24, alphanumeric, count 50
50 tokens, one per line, downloadable as .txt — paste into a SQL INSERT or seed script.
Each token is generated independently with its own crypto.getRandomValues() call — no sequence collision risk.
About Random String Generator
A random string generator creates a sequence of characters drawn from a chosen alphabet — used for passwords, API keys, session tokens, file names, test fixtures, database seeds, and any case where you need a unique, hard-to-guess identifier. The DevPik Random String Generator builds those strings using crypto.getRandomValues(), the browser's cryptographically secure random number generator. That matters: Math.random() is fast and convenient but predictable enough that an attacker who sees one of its outputs can often guess the next one. crypto.getRandomValues() draws from the OS-level entropy pool — the same source used for TLS keys — so the strings it produces are safe to use as secrets. The tool also calculates the entropy bits and crack-time estimate of every string you generate, so you can immediately see whether a 12-character lowercase string (good for a username) is the same strength as a 32-character mixed string (good for an API key). It is not. Bulk mode lets you generate up to 100 strings at once for seeding test databases or pre-generating tokens, and the entire generator runs 100% client-side — strings never leave your browser.
Troubleshooting & Common Issues
The generated string contains characters my system rejects (like quotes or backslash)
Turn off the Symbols toggle and use a custom character set instead. For URL-safe tokens, paste 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_' as the custom character set. For hex-only output, use the Hex String preset.
I want to exclude characters that look alike (0/O, 1/l/I)
Enable the 'Exclude ambiguous (0/O, 1/l/I)' option. This is essential for any string a human will read or type — it prevents costly typos when someone reads a token aloud or copies it from a screen.
I selected 'Exclude duplicates' and got a shorter string than I asked for
Excluding duplicates caps the output at the size of your character set. If you ask for 100 characters from the 10-digit set 0-9, you'll get at most 10 characters — there are only 10 unique digits available. Either widen your character set or turn off the duplicate exclusion.
The same character keeps appearing twice in a row — is the RNG broken?
No — that's actually evidence the RNG is working correctly. True random output produces runs and clusters; biased RNGs produce suspiciously even spacing. If runs look wrong to you, that's the gambler's fallacy at work, not a bug in the tool.
Frequently Asked Questions
Is this random string generator cryptographically secure?
Yes. The tool uses window.crypto.getRandomValues() — the browser's cryptographically secure RNG, backed by the operating system's entropy pool (the same source used for TLS keys, SSH keys, and Web Crypto operations). It is suitable for passwords, API keys, session tokens, and other security-sensitive use cases. We never use Math.random() for any output.
Can I use the output as a password?
Yes — and you should prefer machine-generated passwords over human-chosen ones. A 16-character random string from the all-character-types preset has roughly 105 bits of entropy, which is far stronger than the typical password humans pick. Click the Password preset and you'll get a strong default. Always store passwords in a password manager, never in plain text.
Why is crypto.getRandomValues() better than Math.random()?
Math.random() uses a pseudo-random algorithm (xorshift in V8) that's fast but predictable — given a few outputs, an attacker can recover the internal state and predict every subsequent output. crypto.getRandomValues() pulls from the OS entropy source (e.g. /dev/urandom on Linux, BCryptGenRandom on Windows) which is unpredictable even to the system itself. Use Math.random() for game animations; use crypto.getRandomValues() for anything secret.
How long should an API key be?
The industry baseline is 128 bits of entropy — about 22 alphanumeric characters or 32 hex characters. The OWASP guidance for session IDs is 64 bits minimum, 128 bits recommended. The Token preset (64 chars alphanumeric) gives you over 380 bits of entropy, which is overkill but harmless. If your service stores keys in a database column, longer keys cost essentially nothing to store but make brute-forcing impossible.
What do entropy bits mean?
Entropy bits measure how unpredictable a string is. A string with N bits of entropy could be any one of 2^N possible values. 80 bits ≈ 1 trillion trillion possibilities — currently brute-force-resistant. 128 bits is the cryptographic standard. The bar in the tool reflects this: red below 28 bits, green at 80+, deep green at 128+.
Are the strings I generate stored anywhere?
No. The tool runs entirely in your browser — no string is ever sent to a server, logged, or stored. We have no analytics on the actual content. Once you close the tab, the strings are gone forever (the page also doesn't persist them in localStorage). For workflows where you need to keep a generated value, copy it into a password manager.
How does 'Exclude duplicates' work?
When enabled, the generator picks each character without replacement — once a character has been used, it's removed from the pool for the rest of that string. This is useful when you specifically want every character to be different (some legacy systems require it). Note that it caps the maximum length at the size of your character set.
Can I generate a UUID with this tool?
For UUIDs, use the dedicated UUID Generator instead — UUIDs have a specific 8-4-4-4-12 format and a version marker that this tool won't produce. This generator is for free-form random strings (passwords, API keys, tokens) where length and character set are the main constraints.
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