Type a regular expression and get random strings that match it, ready to use as test data, fixtures or sample IDs. Every string is checked against your browser's own regex engine, and you can set how many to create, how long repeats may grow and a seed for repeatable output.
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Generated strings
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How to use the Regex String Generator
Enter a regular expression without the slashes, or paste a literal like /abc\d+/i and the flags are split off for you.
Or pick a preset such as US phone number, UUID v4 or IPv4 to start from a tested pattern.
Set the amount and the max repetition used for *, + and {n,}.
Click Generate strings. Each result shows a check mark when it fully matches the regex.
Choose an output format and copy or download the list. Add a seed if you need the same list again later.
How each regex part is turned into text
Syntax
What the generator does
Example pattern
Possible output
abc
Copies literal characters
ID-
ID-
[a-f0-9]
Picks one character from the class
[A-F]\d
C7
[^…], .
Picks from the chosen character set, excluding listed characters
[^aeiou ]{4}
x9Q#
\d \w \s
Digit, word character (letter, digit, underscore), a space
\w{3}\s\d
k_2 8
a|b|c
Chooses one alternative with equal chance
(red|green|blue)
green
{n}, {n,m}
Repeats a random number of times inside the range
\d{2,4}
731
* + {n,}
Repeats up to the max repetition setting
x+
xxxx
?
Includes the part or leaves it out
colou?r
color
(…) and \1
Remembers what a group produced and repeats it for the backreference
(\d)-\1
4-4
^ $ \b, (?=…)
Produce no text; checked afterwards with the real regex
^(?=.*\d)\w{6}$
ab3_Zq
Tips for useful test data
Anchor in your app, not here: the generator always produces a string that matches the whole pattern, so ^ and $ are optional.
Prefer explicit classes over .: [a-z0-9]{8} gives cleaner sample values than .{8}, which can include punctuation and spaces.
Use reserved example domains such as example.com, example.org and test addresses for emails and URLs, so generated data can never reach a real inbox or site.
Test the edges: to exercise length limits, generate with a small max repetition and again with a large one, or write the exact bounds as {min,max}.
Make fixtures reproducible: a seed such as fixtures-v1 returns the same list every time, which keeps snapshot tests stable.
To check how a pattern behaves on real text, use the Regex Tester. Looking for a ready-made pattern? Browse the Regex Cheat Sheet. For realistic names, addresses and records, try the Fake Data Generator.
Frequently asked questions
How does a regex string generator work?
It parses the regular expression into its parts (literal characters, character classes, groups, alternatives and quantifiers) and walks that structure, picking a random choice at every decision: one character from each class, one branch of each alternation and a repeat count within each quantifier's range. The result is a string the pattern accepts.
Why is there a maximum repetition setting?
Quantifiers like *, + and {3,} have no upper limit, so a generator must choose one. The max repetition caps how many times an open-ended part repeats: * produces 0 to N copies, + produces 1 to N and {3,} produces 3 to N (or exactly 3 if N is smaller). Fixed ranges such as {2,5} are always respected.
Does it support lookaheads like (?=.*\d)?
Yes, by verification. Lookarounds cannot be generated directly, so the generator builds a candidate from the rest of the pattern and tests it with the real regex, retrying up to 30 times until it passes. Patterns like strong-password rules work well this way; any string that still fails is marked with a cross.
What do . and negated classes like [^a-z] produce?
They pick from the character set you choose: printable ASCII, letters and digits only, or ASCII plus accented Latin letters. Restricting the set keeps test data readable and avoids control characters.
Which regex flavor is supported?
JavaScript (ECMAScript) syntax, which covers the everyday syntax shared with Python, Java, PHP (PCRE) and .NET. Engine-specific extras such as possessive quantifiers, atomic groups or recursion are not supported; the pattern is first compiled by your browser, so unsupported syntax produces a clear error.
Can I get the same strings again?
Yes. Enter any text in the Seed box and the generator uses a deterministic random sequence, so the same pattern, settings and seed always produce the same list. Leave it empty to use your browser's cryptographic random generator.
Why did I get fewer unique strings than I asked for?
Some patterns allow only a few distinct values. For example, [ab]{2} has just four possible strings, so asking for 20 unique results returns those four. Untick Unique strings only to allow repeats.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.