Code
Test regular expressions against sample text with match highlighting.
Runs entirely in your browser
Nothing you paste is uploaded. Monaco and Prettier load on demand from this origin.
Pattern
Live match highlighting below
Sample text
Matches
Call 555-0199 or 555-0242 today.
555-0199555-0242There is no upload endpoint — your files are processed in this browser tab. Open your network tab and check. See how it stays private.
How to regex tester
- Enter a pattern. Type your regular expression and set flags like global, case-insensitive, or multiline.
- Paste test text. Add the sample text you want to match against.
- See live matches. Matches highlight as you type, with capture groups broken out.
- Use it. Copy the working pattern into your code once it behaves.
A regex tester is where you build a pattern safely before dropping it into code that runs against real data. Live highlighting turns the usual guesswork — why does this match too much? why does it skip that line? — into something you can see immediately.
Toggle flags to understand their effect, watch capture groups populate, and iterate until the pattern does exactly what you intend. Because it is JavaScript regex, it mirrors what you will get in the browser or Node.
For extracting many matches out of a big document, use the Data Zone regex extraction tool; for a quick syntax refresher, see the regex cheatsheet.
Frequently asked questions
Which regex flavor is this?
JavaScript (ECMAScript) regular expressions, matching what runs in browsers and Node — mind the small differences from PCRE or Python.
What do the flags do?
'g' finds all matches, 'i' ignores case, 'm' makes ^ and $ match line boundaries, and 's' lets '.' match newlines.
Can I see capture groups?
Yes. Each match shows its numbered (and named) capture groups so you can confirm what you are extracting.
Is my test text uploaded?
No. Matching runs in your browser tab; your patterns and sample data stay on your device.