Runs the pattern against the test string in your browser using JavaScript's RegExp engine. Returns the match count and every match with its character position. Nothing is sent to a server.
Calculation details
Planning estimate only, not financial, tax, or legal advice. Verify assumptions and current rules before making decisions.
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Use this result
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What does this calculator estimate?
The pattern \d{3}-\d{2}-\d{4} matches 123-45-6789 inside mixed text. The tester shows matches, groups, and non-matches in real time.
- \d matches any digit; {3} repeats it three times (Wikipedia).
- Regex groups capture sub-parts for extraction.
- Real-time testing catches escaping errors before they reach production.
What regex testing is for
Regular expressions are the standard way to find and extract patterns in text — validation, search, and data cleaning. The tester shows exactly what a pattern matches, which groups it captures, and where it fails.
Limitations to watch for
Regex syntax differs slightly across engines (JavaScript, Python, PCRE). The tool follows JavaScript conventions. Anchors (^ $) and flags (g, i) change behavior — test with the flags you'll use in code.
How to use it in practice
Write the pattern, paste sample text, and watch the matches highlight. Verify capture groups extract the parts you need. Test edge cases — empty strings, unexpected formats — before deploying the pattern.
['Enter the regex pattern.', 'Enter the sample text.', 'Read the matches and groups.']
How this calculator works
Formula
Tests a regular expression pattern against sample text, showing matches, groups, and non-matches in real time.
Worked example
The pattern \d{3}-\d{2}-\d{4} matches 123-45-6789 in a text of mixed content.
Assumptions to verify
- JavaScript regex syntax applies.
- The sample text represents real input.
- Flags are applied as the user expects.
Frequently asked questions
What is a regex tester?
A tool that runs a regular expression against sample text and shows what matches.
How do I use it?
Enter the pattern and text — the tool highlights matches and shows capture groups.
What regex syntax does it use?
JavaScript-style syntax, the common baseline for web and node tooling.
What are capture groups?
Parenthesized parts of the pattern that extract specific substrings: (\d{3}) captures the area code.
Why is my pattern not matching?
Check anchors, flags, escaping, and whether the pattern matches the actual text format.
What are common uses?
Email/phone validation, log parsing, search-and-replace, and data extraction.
Does it work in Python?
Mostly — Python adds minor differences; verify portability.
Cite this tool
BoringToolsKit. “Regex Tester.” boringtoolskit.com/regex-tester/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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