Developer Suite• Testing & Utils
Regex Tester
Build, test, and debug regular expressions with live highlighting.
Valid Pattern
//
Test String
Match Results (0)
No matches found.
What is this tool?
An interactive Regular Expression testing environment that highlights matches in real-time within your test string, supporting custom flags and capturing groups.
How to test Regular Expressions
- Type your Regular Expression pattern into the top input field.
- Toggle specific Regex flags (g, i, m) as needed.
- Paste your test text into the main editor area.
- Matches and capturing groups will be highlighted automatically as you type.
Key Features
- Real-time expression evaluation and highlighting
- Support for global (g), case-insensitive (i), and multiline (m) flags
- Detailed breakdown of exact matches and capture groups
- Safe execution environment to prevent catastrophic backtracking crashes
Frequently Asked Questions
Which Regex engine does this use?
The tool leverages the native JavaScript (ECMAScript) RegExp engine built directly into your web browser.
What happens if I write a catastrophic backtracking expression?
Because the expression evaluates directly in your browser's main thread, an infinitely looping regex may freeze the application tab. The tool implements basic debouncing to mitigate partial-typing freezes.
Privacy First
Evaluation executes entirely within the browser's native JavaScript engine. Your patterns and test strings are never sent to a server.