Test, debug, and write Regular Expressions with real-time highlighting and match counting.
Writing a regular expression often takes several rounds of trial and error, and without instant visual feedback, it's genuinely hard to know whether your pattern is matching what you intended or quietly matching nothing at all. Our Regex Tester removes that guesswork by highlighting every match directly within your test text as you type, letting you see exactly what your pattern catches in real time. Since this Regex Tester processes everything locally inside your browser, your test data and patterns are never sent to an external server.
Using the Regex Tester starts with entering your pattern into the regex bar at the top, styled with the familiar forward-slash delimiters developers expect, along with a separate field for flags like g, i, or m. Below that, paste your test string into the left panel, and the right panel instantly displays your text with every match visually highlighted using alternating color tags, making it immediately obvious which portions of your text the pattern actually captures.
What makes this Regex Tester genuinely useful beyond basic pattern matching is the live match counter that updates instantly alongside the highlighted results, showing you exactly how many matches your current pattern produces. This immediate numerical feedback, combined with the visual highlighting, lets you quickly iterate on a pattern, tightening or loosening it until you get exactly the match count and matched substrings you expect, without needing to run code or check a console.
For developers who don't write regex daily and need a quick starting point, this Regex Tester includes a dropdown of pre-built patterns covering some of the most commonly needed validation cases: email addresses, URLs, strong passwords, international phone numbers, and HTML tags. Selecting any preset instantly populates both the pattern and flag fields with a working, tested expression, which you can then study, modify, or use directly, saving you from looking up common regex patterns from scratch every time.
If your pattern contains a syntax error, this Regex Tester immediately surfaces the actual JavaScript regex engine's error message rather than silently failing, helping you pinpoint exactly what's wrong with your expression. Because everything runs through the browser's native RegExp engine, there's no signup, no file size limits, and instant updates as you type. It's a genuinely practical utility for developers, QA engineers, and anyone who regularly works with pattern matching and needs a fast, visual way to test regular expressions, completely free.