Regex tester
Write a regular expression and see every match highlighted as you type, with capture groups, named groups and a replace preview. Uses JavaScript’s regex engine, in your browser.
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How it works
- 1
Write the pattern
Type it without slashes and switch flags on or off: global, ignore case, multiline, dot-all, unicode and sticky. Syntax errors are explained as you type.
- 2
Paste test text
Matches are highlighted in place and listed below with their position and every capture group, numbered and named.
- 3
Try a replacement
Use $1,
lt;name> and amp; to preview what String.replace would produce, then copy the result.
Questions
- Which regex flavor is this?
- JavaScript (ECMAScript), as in Chrome, Node.js and every browser. It is close to PCRE for everyday patterns; lookbehind, named groups and \p{…} Unicode classes all work.
- Why does my pattern freeze other testers?
- Patterns like (a+)+$ can take exponential time on some inputs (catastrophic backtracking). Here the regex runs in a background worker and is stopped after 1.5 seconds, so the page stays responsive and you’re told why.
- How many matches are shown?
- Up to 10,000, which is enough for any text you’d check by eye. The count tells you if there are more.
- Is my text uploaded?
- No. Matching happens in this tab.