๐งช Regex Tester
Test and debug regular expressions free online with live match highlighting. Supports flags and capture groups, no upload.
๐งช Regex Tester
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About the Regex Tester Tool
Regular expressions are powerful and famously difficult to get right. A pattern that looks correct frequently matches more or less than intended, and the failure is usually silent โ the code runs, it just processes the wrong things.
Testing interactively against real sample text is the only reliable way to develop them. Seeing exactly what matches, and what your capture groups contain, turns pattern writing from guesswork into iteration. This tester runs entirely in your browser using the JavaScript regex engine.
How to Use Regex Tester
- Enter your regular expression pattern.
- Set the flags you need โ global, case-insensitive, multiline.
- Paste sample text into the test area.
- Review the highlighted matches and captured groups.
When to Use This Tool
- Developing a validation pattern for email addresses or phone numbers
- Building an extraction pattern for parsing log files
- Debugging a pattern that matches too much or too little
- Testing search and replace patterns before applying them
- Learning regex syntax through immediate feedback
Things Worth Knowing
- This uses the JavaScript regex engine. PCRE, Python, and Java differ in some syntax and features.
- The global flag finds all matches; without it, only the first is returned.
- Quantifiers are greedy by default โ add ? to make them lazy.
Quick Facts
| Tool name | Regex Tester |
| Category | Utilities |
| Price | Free โ no account, no trial, no watermark |
| Where it runs | Entirely in your browser (client-side) |
| Files uploaded | None โ your data never leaves your device |
| File size limit | None imposed; limited only by device memory |
| Works offline | Yes, once the page has loaded |
| Platforms | Windows, macOS, Linux, Android, iOS |
Frequently Asked Questions
What is the difference between greedy and lazy matching?
Greedy quantifiers match as much as possible, then backtrack. Lazy ones, written with a trailing ?, match as little as possible. With input , the pattern <.*> matches the whole string while <.*?> matches just .
Why does my pattern not work in Python?
Regex flavours differ. JavaScript lacks lookbehind in older engines, uses different named group syntax historically, and handles Unicode properties differently. Test in the environment you will deploy to.
How do I match a literal dot or bracket?
Escape it with a backslash. Characters such as . * + ? ( ) [ ] { } ^ $ | \ have special meaning and must be escaped to match literally.
Should I use regex to validate email addresses?
A simple pattern catches obvious typos, but fully correct email validation per the specification is notoriously impractical. The reliable check is sending a confirmation message to the address.