Key takeaways
- Regex Tester highlights every match in your sample text live, as you edit the pattern.
- Testing a pattern against real sample text before dropping it into code catches mistakes faster than trial-and-error in your editor.
- Useful for validating input formats (emails, phone numbers), extracting data, and understanding someone else's regex.
- Everything runs in your browser using standard JavaScript regex syntax.
Testing a pattern
Open Regex Tester, paste in sample text that represents what you're matching against, then type your pattern — matches highlight live as you adjust it, so you can see immediately whether a tweak made things better or worse.
Getting useful test coverage
- Include edge cases in your sample text, not just the obvious match — an email with a plus sign, a phone number with dashes, whatever variation you expect to actually see.
- Add a case your pattern should reject, to confirm it's not matching too broadly.
- Build it up gradually — start with the simplest version of the pattern and add complexity piece by piece, checking the highlights after each change.
Frequently asked questions
Does it support capture groups?
Yes — standard JavaScript regex syntax, including groups, is supported.
Why does my pattern work here but not in my code?
Regex flavors differ slightly between languages (Python, PHP, JavaScript). This tool uses JavaScript's regex engine, so a pattern using syntax specific to another language may behave differently there.