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Regex Tester
Test and debug regular expressions with live matching and highlights
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What is Regex Tester?
Test regular expressions against sample text with real-time match highlighting. Enter your regex pattern and flags, then see all matches highlighted instantly in your test string. The tool shows detailed match information including capture groups, indices, and match count. Perfect for building and debugging regex patterns for JavaScript, Python, or any language that supports standard regex syntax.
How to Use Regex Tester
- 1Enter your regular expression pattern in the pattern field
- 2Select the flags you need: global (g), case-insensitive (i), multiline (m), dotAll (s)
- 3Type or paste your test string in the text area below
- 4See matches highlighted in real time with detailed match information
Frequently Asked Questions
This tool uses JavaScript's built-in RegExp engine. JavaScript regex supports most standard features including character classes, quantifiers, lookahead/lookbehind, named capture groups, and Unicode escapes. The syntax is compatible with most other regex flavors.
The 'g' flag enables global matching (find all matches, not just the first). The 'i' flag makes matching case-insensitive. The 'm' flag makes ^ and $ match line boundaries instead of string boundaries. The 's' flag makes the dot (.) match newline characters.
Most regex syntax is shared across languages (JavaScript, Python, Java, PHP, etc.). However, some advanced features like possessive quantifiers or conditionals may differ. This tool is best for testing standard patterns that work across all major languages.
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