JavaScript Regex Tester - Regex Replace, Flags and Capture Groups
Test JavaScript regular expressions, flags, matches, capture groups, named groups, highlights, and replacement output online. Replace text in-place and copy results fast.
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Regular Expression Tester: popular Google search intents
Most visitors search for regex tester online, JavaScript regex tester, regex replace online, regex capture groups tester, named capture groups regex, regex flags, and regex match highlighter. The page keeps pattern, replacement, test text, Test Regex, Replace, Copy Result, and report copy before flags and reference details, so mobile users can test, replace, and copy without scrolling through documentation first.
What this tool is for
Paste test text and a JavaScript regular expression, check matches, flags, capture groups, named groups, and replacement output, then tap Replace to write the result back into the same test text box for fast mobile copy. Advanced options keep flags, separate output, and regex reference details available below the first-screen controls.
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Frequently asked questions
Is Regular Expression Tester free?
Yes. ToolNest provides Regular Expression Tester as a free browser-based utility.
Does Regular Expression Tester require an account?
No account is required. Open the tool and use it directly in your browser.
Does Regular Expression Tester support JavaScript regex flags?
Yes. It uses JavaScript regular expressions and supports common flags such as global, ignore case, multiline, dotAll, and Unicode. The default flags are available in Advanced options so they do not block the main mobile workflow.
Can Regular Expression Tester test capture groups and named groups?
Yes. Match tables show numbered capture groups and named capture groups, and the report can be copied as CSV for debugging regex behavior.
Does Regular Expression Tester replace text in the same box?
Yes. Tapping Replace writes the replacement output back into the test text box by default for fast copy. A separate replacement output box is available when you want to compare original and replaced text.
How do I use Regular Expression Tester?
Open the Regular Expression Tester page, enter or paste your values, use the visible controls, and copy the result from the first working area. It is grouped with Developer Tools for quick browsing.
Can I copy results from Regular Expression Tester?
Yes. ToolNest tools are designed around copy-ready output, so you can reuse the result in documents, spreadsheets, code editors, forms, or messages without creating an account.