RegEx Tester
Developer UtilitiesTest regular expressions against sample text with live highlights.
Test text
Highlighted matches (0)
Matches light up here as you type a pattern and test text.
Match list
Each match appears here with its position and capture groups.
Pattern breakdown
Type a pattern above to see each construct explained in plain English.
Cheat sheet
Character Classes
.Any character except newline\dDigit, 0 to 9\wWord character: letter, digit, underscore\sWhitespace: space, tab, newline\D \W \SNegated versions of the above[abc]One of a, b, or c[^abc]Any character except a, b, or c[a-z0-9]Character in a range
Anchors
^Start of string, or line with m flag$End of string, or line with m flag\bWord boundary\BNot a word boundary
Quantifiers
*Zero or more times+One or more times?Zero or one time, optional{3}Exactly 3 times{2,}2 or more times{2,5}Between 2 and 5 times+? *? ??Lazy: match as little as possible
Groups & Lookaround
(abc)Capturing group(?:abc)Non-capturing group(?<name>abc)Named capturing group\1Backreference to group 1a|bMatch a or b(?=abc)Lookahead: followed by abc(?!abc)Negative lookahead: not followed by abc(?<=abc)Lookbehind: preceded by abc(?<!abc)Negative lookbehind: not preceded by abc
What is RegEx Tester?
RegEx Tester lets you build and check regular expressions with live match highlighting, a full match list, and a plain-English breakdown of your pattern. Type an expression, toggle the flags you need, and see every match light up in your test text as you go — capture groups and named groups included. A built-in cheat sheet keeps the syntax within reach. It all runs in your browser, so your text is never uploaded.
How to use RegEx Tester
3 simple steps to complete your task directly in your browser:
Enter a pattern
Type your regular expression in the Pattern field, or click Load sample to try an email-matching example. An invalid pattern shows a clear error message instead of failing silently.
Toggle flags
Switch g, i, m, s, u, and y on or off with the flag buttons — each has a tooltip explaining what it does, from global and ignore-case to multiline and unicode.
Add test text
Paste the text you want to search in the Test text box. Matches highlight instantly in the panel beside it, so you can see exactly what your pattern catches.
Common uses
- Test a pattern before pasting it into your code
- Debug why a regex is matching too much or too little
- Extract and verify capture groups from sample data
- Learn regex syntax with live feedback and the cheat sheet
- Validate an email, URL, or ID format against real examples
- Understand an unfamiliar pattern via the plain-English breakdown
Why choose VersaTools
100% private
Your files are processed inside your browser and are never uploaded to a server.
Free, no account
No sign-up, no watermark, no paywalled “premium” tier. Just open a tool and use it.
Instant
No upload, no queue, no server round-trip — work starts the moment you drop a file.
Runs in your browser
Built on open web standards. Works on any modern desktop browser, nothing to install.
No upload size caps
Nothing leaves your device, so there’s no server file-size limit — only your machine’s memory.
Yours to keep
Results download straight to your device in clean, standard file formats.