Regex Tester
Test and debug regular expressions with live matching.
How to use this tool
- Enter your regex pattern in the pattern field.
- Set the flags (g for global, i for case-insensitive, m for multiline).
- Enter your test string in the text area.
- View matches highlighted in real-time.
- Copy the pattern for use in your code.
About this tool
Regex Tester is an online, free tool that helps developers create and debug regular expressions. No registration required! Test patterns against sample text and see matches highlighted in real-time. Supports JavaScript regex syntax with flags for global, case-insensitive, and multiline matching. Essential for form validation, text parsing, and data extraction tasks.
Frequently asked questions
How do I test a regular expression?
Type the pattern into the pattern field, set the flags you need, and paste sample text below. Matches highlight as you type, so you can adjust the pattern and watch what it catches without running any code.
What do the g, i and m flags do?
g is global, which finds every match rather than stopping at the first. i makes the match case-insensitive. m is multiline, which changes ^ and $ so they anchor to the start and end of each line instead of the whole string.
Why does my pattern match nothing?
Most often an unescaped metacharacter. The characters . * + ? ^ $ ( ) [ ] { } | \ all have special meaning, so to match one literally put a backslash in front of it. A full stop matches any character until you write it as \. instead.
What is the difference between greedy and lazy matching?
A greedy quantifier such as .* takes as much text as it can and then gives characters back until the rest of the pattern fits, so it happily swallows everything between the first and last delimiter. Adding a question mark makes it lazy, so .*? takes as little as possible. Lazy is almost always what you want when matching between two markers.
Which regex dialect does this use?
JavaScript's, which is what runs in the browser. It is close to but not identical to PCRE, Python or Java: lookbehind support varies by browser version, and named groups and Unicode property escapes need the right syntax. Patterns that work here will usually port, but verify anything exotic in your target language.
Is my test data private?
Yes. The pattern and the sample text stay in your browser and are evaluated there. Nothing is uploaded or stored.