Regex Tester & Debugger
Test regular expressions with real-time match highlighting and group capture. Includes common regex patterns reference. Free online regex testing tool.
Why Use a Regex Tester?
Regular expressions are powerful but notoriously difficult to get right. A regex tester lets you experiment with patterns in real-time, seeing exactly what matches and what doesn't. Our tool provides instant visual feedback with match highlighting, captured groups display, and a library of common patterns to get you started quickly.
Key Features
- Real-time match highlighting in the test string
- Match groups and capture display
- 8 common regex patterns with one-click load
How to Use
- Enter your regex pattern and select flags (g, i, m, s)
- Type or paste the test string to match against
- View highlighted matches and captured groups below
Technical Details
The regex engine uses JavaScript's built-in RegExp object. The global (g) flag uses iterative exec() calls to find all matches. Groups are extracted from the match result array. Highlighting is done by wrapping matched segments in mark elements. All processing is client-side — no regex data is sent anywhere.
FAQ
What regex features are supported?
The tool supports all JavaScript regex features including character classes, quantifiers, groups, lookaheads, lookbehinds, and Unicode property escapes.
What do the flags mean?
g = global (find all matches), i = case-insensitive, m = multiline (^ and $ match line boundaries), s = dotAll (. matches newlines).
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