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Regex tester
Test a regular expression against your own text and see every match highlighted as you type. A table lists each match with its position and capture groups, named groups included. It uses JavaScript regex and runs in your browser.
How to test a regular expression
- 1Type your pattern between the slashes
- 2Paste your test text and tick the flags you need
- 3Read the highlighted matches and the group table
- Highlighted matches and a table of groups.
What you get
- Live as you type.Matches, groups and errors update with every keystroke.
- Groups in colour.Each capture group has its own colour in the text and in the table.
- Nothing is uploaded.Pattern and text stay in your browser, on your device.
What you can do
- Highlight every match in the test text, and count the matches and groups.
- List each match in a table with its number, text and position, and one column per group, named groups by name.
- Switch the flags g, i, m, s, u and y on and off, each with a short explanation.
- Show an explanation of the pattern in plain English, and a replace preview, in the other two views of the same tool.
- Load a ready-made pattern from "Common patterns", such as email, URL or IPv4.
Good to know
- The tool uses the JavaScript regex flavour. Lookbehind and named groups work, but PCRE-only features such as possessive quantifiers do not.
- The text shows up to 2000 matches and the table the first 200.
- An invalid pattern shows the browser's own error message instead of matches.
- Positions are counted in characters from 0, as JavaScript counts them.
Questions
How do I test a regex online?
Type the pattern in the box between the slashes, paste your text below it and tick the flags. Matches are highlighted at once.
Which regex flavour does it use?
JavaScript, the engine of your browser. That fits code for the web and Node.js, but check the details if you use Python, PHP or Java.
How do I see the capture groups?
Each group has its own colour in the text, and the table below has one column per group. Named groups use their name as the header.
Is my text uploaded?
No. Matching runs in your browser, so logs and other private text stay on your device.