Also available in the Chrome extension Every Zase tool also lives in the free Developer Toolkit by Zase extension: fully offline, in a window or the side panel, one keyboard shortcut away.
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About this Regex Tester
The Regex Tester lets you build a regular expression and watch it work: matches highlight in your test text as you type, capture groups are listed, flags can be toggled, and replacements can be previewed. It runs the JavaScript regex engine, so what you test is what your code runs.
How to use the Regex Tester
- Write your pattern and set the flags you need.
- Paste test text and inspect the highlighted matches and groups.
- Add a replacement string to preview substitutions before you ship them.
Good to know
- A small built-in example library covers common jobs like emails, URLs and dates.
- Test the awkward cases on purpose: empty strings, unicode and text that should NOT match.
- Greedy versus lazy quantifiers explain most regex surprises; the group view makes them visible.