Input validation
Verify email, slug, date, and identifier patterns before moving them into production code.
Regex Tester
Test JavaScript regular expressions, inspect matches, and preview replacement output with a focused browser-based workflow.
Matches
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Replacement output
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How to use this tool
A quick workflow so you can get the result you need without guesswork.
- 1
Enter a regular expression pattern and choose any flags you want to apply.
- 2
Paste or type the test text into the large editor.
- 3
Run the matcher to inspect matches, captured substrings, and optional replacement output.
Useful examples
Practical cases where this utility saves time and reduces mistakes.
Search and replace design
Prototype replacement expressions and confirm capture groups against realistic sample text.
Debug support tickets
Test log or payload patterns quickly when investigating malformed data in the browser.
Frequently asked questions
Short answers to the most common questions about the calculator above.
Which regex flags are supported?
The tester supports the standard JavaScript flags such as g, i, m, s, u, d, and y when available in your browser.
Can I test replacements as well as matches?
Yes. Enter replacement text and the tool will show the transformed output using the same pattern and flags.
Does this regex tester use JavaScript regex syntax?
Yes. Patterns are executed with the JavaScript RegExp engine available in your browser.
Can I inspect multiple matches?
Yes. When you enable the global flag, the tester lists every match and its index within the input text.
Test JavaScript Regular Expressions Online
This regex tester lets you try JavaScript regular expressions against sample text without opening a code editor. Enter a pattern, choose flags, and inspect every match along with its position and captured groups. That makes it useful for pattern design, quick debugging, and search-and-replace experiments.
The tool also includes replacement output, which is important when you are designing transformations and not just matches. It helps confirm that your pattern and replacement string work together as expected.
Helpful for Validation, Parsing, and Cleanup Work
Regex shows up in form validation, data cleanup, log parsing, and text transformation. A dedicated browser-based tester is often the fastest place to verify a pattern before you commit it to application code or a script.
Because the page is focused and local, you can iterate on complex expressions quickly while keeping sample data under your control.
Related tools
Keep moving with other free browser-based utilities on HandyUtils.