Regex Tester
Test, debug, and validate Regular Expressions against sample text with live match highlighting and capture group inspection.
100% In-Browser Privacy: This tool operates directly in your browser. None of your input text, documents, calculation values, or images are ever transmitted to or stored on our servers.
How to Use the Regex Tester
Enter your regular expression pattern in the regex field.
Configure regex flags: Global (g), Case-insensitive (i), Multiline (m), DotAll (s).
Paste target test string in the text editor.
Inspect highlighted matches, character indices, and capture group tables.
Worked Example & Demonstration
Regex: [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}
Text: Contact info@itemarketplus.com today.Match 1: info@itemarketplus.com at index 8
Technical Method & Underlying Formula
Live evaluation using standard JavaScript RegExp engine with matchAll iteration and execution time guards.
Operational Boundaries: Guarded against catastrophic backtracking with input length and execution duration timeouts.
Frequently Asked Questions
What do the regex flags mean?
g = global match, i = ignore case, m = multiline (^ and $ match line starts/ends), s = dot matches newlines.
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