About the Random String Generator
Make random strings of letters, numbers and symbols for test data, coupon codes, API keys, file names or temporary passwords. Choose the length, how many you need and which characters to use.
Each string shows how hard it would be to guess, and you can copy the whole list or download it as a text file.
How it works
Every character is picked by your browser's cryptographically secure random generator, the same kind used for encryption keys, not by a predictable formula. Each character you allow has exactly the same chance at every position: the few random numbers that would favour some characters over others are thrown away and drawn again.
With 'At least one character from each set', a string that misses a set is thrown away as a whole and a new one is made. That keeps every string that follows the rule equally likely, instead of forcing characters into fixed places.
The strength shown is the exact number of different strings your settings can produce, written as bits: each extra bit doubles the number of guesses someone would need. A 16-character string of letters and numbers has about 95 bits.
Assumptions and limits
- Each character counts once, even if it is in a set and also typed in your own characters. Spaces are never used.
- 'Leave out look-alikes' removes 0, O, o, 1, l, I and |, which are easy to misread when a code is typed by hand.
- 'No repeated characters' means no character appears twice inside one string; different strings in the list can still share characters.
Worked examples
Coupon codes
Choose uppercase and numbers, leave out look-alikes, length 8 and how many 50: you get 50 codes like 7KQ2X9MZ that are easy to read out and type.
An API key
Letters and numbers with length 32 gives about 190 bits, far beyond what can be guessed by trying.
Test IDs in hex
Untick all sets and type 0123456789abcdef as your own characters for hex strings of any length.
How to use the Random String Generator
- Set the length. And how many strings you need.
- Pick the characters. Letters, numbers, symbols or your own.
- Generate and copy. Copy the list or download it as .txt.
Frequently asked questions
Are these strings really random?
They come from the secure random generator built into your browser, which is designed for encryption keys. Every allowed character is equally likely at every position, and the tests behind this page check that over hundreds of thousands of characters.
How long should a random string be?
For anything that protects an account or data, aim for at least 80 bits, which is about 14 letters and numbers. Short codes that expire quickly, like a one-time voucher, can be shorter. The bits shown update as you change the settings.
Can I use this as a password generator?
Yes: tick all four sets and choose 16 or more characters. For passwords you have to remember, a passphrase of several random words is easier to type; for passwords kept in a password manager, a random string is ideal.
Will the same string come up twice?
It is possible but, for sensible lengths, extraordinarily unlikely. With 16 letters and numbers there are about 48 billion billion billion possible strings, so even millions of them almost never collide.
Is anything sent to a server?
No. The strings are made on your own device and are not stored, logged or uploaded, so nobody else, including us, ever sees them. Reloading the page or closing the tab clears them.
This tool runs entirely in your browser. What you enter or upload stays on your device and is never sent to our servers.