Regex Tester
Test and debug regular expressions with live matching
Regex Tester is a free online tool from BrowserUtils that test and debug regular expressions with live matching. It runs entirely in your browser — your data never leaves your device. No account required.
//g
How to use Regex Tester
- 1 Paste or type your input into the editor above.
- 2 The tool processes your data instantly — right in your browser, with nothing sent to a server.
- 3 Copy the result with one click or continue editing your input.
About Regex Tester
Free online regex tester. Write regular expressions and test them against sample text with real-time match highlighting. This tool runs entirely in your browser — your data is never sent to a server. Just paste your input, get instant results, and copy with one click. No sign-up or installation required.
Regex Tester specs
- Runtime
- 100% client-side (browser)
- Built on
- Native JavaScript String, Intl.Segmenter, and RegExp APIs with full Unicode support
- Cost
- Free — no account, no rate limits, no usage caps
- Browser support
- Chrome 90+, Firefox 88+, Safari 14+, Edge 90+
- Part of
- 299 developer tools on BrowserUtils (100% client-side)
Questions
What regex flavour does this use?
This tool uses JavaScript regular expressions (ECMAScript specification), which is the same engine used in web browsers and Node.js.
How do I test a regular expression against sample text?
Type your regex pattern in the pattern field and paste sample text below it. All matches are highlighted in real time as you type, so you can iterate quickly.
Does the regex tester support flags like global and case-insensitive?
Yes, you can toggle common flags including global (g), case-insensitive (i), multiline (m), dotAll (s), and Unicode (u) using the flag checkboxes.
Is the regex tester safe for testing patterns with sensitive data?
Yes, all matching runs locally in your browser. Your patterns and test strings are never sent to any server.
Why does my regex work here but not in Python or PHP?
Different languages have slightly different regex engines. JavaScript regex lacks some features found in PCRE (used by PHP and Python), such as lookbehind of variable length and possessive quantifiers.
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