What do the regex flags mean?

"g" finds all matches rather than stopping at the first; "i" ignores case differences; "m" treats beginning and end characters (^ and $) as working across individual lines.

What happens if my regex is syntactically invalid?

The tool safely catches syntax exceptions and displays an informative error badge without crashing.

Dev Tools

RegEx Tester

Test and debug regular expressions with live matches.

100% Private & Client-Side Execution

Pattern matching runs locally. Test data is never logged or transmitted.

About RegEx Tester

RegEx Tester provides an interactive environment to test, build, and debug regular expressions against custom test strings with live visual match highlighting.

How to Use RegEx Tester

Enter your regular expression pattern in the pattern input (without enclosing slashes).
Toggle regex flags: "g" (global), "i" (case-insensitive), or "m" (multiline).
Enter test text in the test string area.
Inspect highlighted match segments and the total match count.

Common Real-World Use Cases

Full Stack Developers: Verify email, phone number, and postal code validation patterns before committing code.
Data Analysts: Test complex extraction patterns for log parsing and text scrubbing.
Technical Students: Learn and master regular expressions with instant visual feedback.

Technical Specifications & Limitations

Runs the native JavaScript RegExp engine in your browser, supporting lookahead, lookbehind, and capture groups.

Frequently Asked Questions

What do the regex flags mean?: "g" finds all matches rather than stopping at the first; "i" ignores case differences; "m" treats beginning and end characters (^ and $) as working across individual lines.
What happens if my regex is syntactically invalid?: The tool safely catches syntax exceptions and displays an informative error badge without crashing.