Regex Tester
Test regular expressions instantly in your browser — enter a pattern, pick your flags, and see matches highlighted live.
- Test String Characters
- 0
- Match Count
- 0
Common Regex Patterns
Your regex and test data are processed locally in your browser and never uploaded or sent to a server.
CleanTextly's Regex Tester lets you test regular expressions instantly in your browser. Enter a pattern, choose your flags, and paste a test string — matches are highlighted live, along with their positions and capture groups, so you can check a regex or debug why it isn't matching without leaving the page. This is a JavaScript regex tester: patterns run through the browser's native RegExp engine, so syntax matches what you'd use in JavaScript or Node.js rather than PCRE, Python, or .NET regex.
Features
Live Match Highlighting
Matches are highlighted directly in your test string as you type, so you can see exactly what your pattern does and doesn't catch.
All Standard JavaScript Flags
Toggle g (global), i (case insensitive), m (multiline), s (dot all), and u (Unicode) independently to test how each one changes the result.
Match Details & Positions
Every match shows its matched text and start/end position in the string, so you can check a regex or debug a pattern with precision.
Capture Groups, Including Named Groups
Numbered capture groups and named groups like (?<username>...) are broken out individually for every match, not just the overall match text.
Clear Error Messages
An invalid pattern — an unterminated character class, an unmatched parenthesis, and similar — shows a specific, readable error instead of crashing or failing silently.
100% Private
Your regex and test data are processed locally in your browser using JavaScript's built-in RegExp engine — nothing is ever sent to a server.
How to Use
- 1
Enter your pattern
Type a regular expression into the Regex Pattern field — just the pattern itself, no need to wrap it in slashes like /pattern/.
- 2
Choose your flags
Check g to find every match instead of just the first, and add i, m, s, or u as your pattern needs.
- 3
Paste your test string
Add the text you want to check the regex against into the Test String box.
- 4
Review the matches
Matches are highlighted instantly, with match count, positions, and any capture groups listed below.
Example
Matching Email Addresses
Pattern (with the g flag)
[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}Test String
Contact john@example.com or jane@test.org for details.
Common Use Cases
Checking a Regex Before Using It
Test a pattern against real examples before pasting it into your code, to confirm it matches what you expect and nothing else.
Debugging Why a Pattern Doesn't Match
See exactly which parts of your test string a regex catches, so you can spot a missing flag or an overly strict pattern quickly.
Extracting Data with Capture Groups
Use capture groups to check how a pattern splits a match into parts — like a username and domain from an email address — before wiring it into a script.
Validating Input Formats
Test whether values like usernames, dates, or hex colors match an expected pattern using the built-in common regex presets as a starting point.
Frequently Asked Questions
A regex tester is a tool that runs a regular expression against a piece of text and shows you which parts of the text it matches, so you can check whether a pattern works as intended.
Enter your pattern into the Regex Pattern field, choose any flags you need, and paste text into the Test String box — matches are highlighted instantly as you type.
CleanTextly's Regex Tester runs entirely in your browser, so you can test a pattern online without installing anything or sending your data anywhere.
Enter the pattern and paste the string into Test String. If the pattern matches, it's highlighted and listed under Match Details; "No matches found" means it doesn't match.
This tool uses JavaScript's native RegExp engine — the same regex flavor used in browsers and Node.js. Syntax can differ from PCRE, Python, or .NET regular expressions.
With the g (global) flag, the tool finds and highlights every match in the test string. Without it, only the first match is shown, matching how JavaScript's RegExp behaves by default.
Yes. Like every tool on CleanTextly, it's completely free to use with no sign-up required.
No. Your regex and test data are processed locally in your browser using JavaScript's built-in RegExp engine — nothing is ever uploaded, logged, or sent to a server.