Regex Tester
Test JavaScript regular expressions and capture groups.
In short
Test JavaScript regular expressions and capture groups.
Formula: Uses the browser's JavaScript RegExp engine and reports match ranges and capture groups.
Your input is processed locally in your browser. It is not saved, logged, or sent with analytics.
Matches
Enter a value to begin.
What this calculator does
Run a pattern against text locally and inspect matches, ranges, and capture groups.
Use it to turn Regular expression, Test text into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this developer tools calculation.
Inputs and what they mean
- Regular expression
- — text value.
- Test text
- — text value.
How to use it
- Paste or enter content in the editor.
- Adjust any options for the result you need.
- Copy or download the locally processed output.
Formula
Uses the browser's JavaScript RegExp engine and reports match ranges and capture groups.
Inputs used: Regular expression, Test text.
Worked example
Find capitalized words
- Start with Regular expression: \b[A-Z][a-z]+\b, Test text: Hello from Free Calculator.
- Apply the method: Uses the browser's JavaScript RegExp engine and reports match ranges and capture groups.
- Match capitalized words and inspect their positions.
Reading the result
The matches appears in the output box and can be copied straight out. Nothing you paste leaves your browser.
Limitations and assumptions
- The result depends on the values you enter for this regex tester; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Common questions
Is my input uploaded?
No. Your input is processed locally in your browser and is not sent to the server or included in analytics.
Can I use the regex tester output elsewhere?
Yes. Use Copy, or Download when available, after reviewing the output.
How do I use the Regex Tester?
Enter the required values for Regular expression, Test text. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Regex Tester use?
Uses the browser's JavaScript RegExp engine and reports match ranges and capture groups. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Regex Tester be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Cite this page
Free Calculator. (n.d.). Regex Tester. https://freecalculator.tech/tools/regex-tester
"Regex Tester." Free Calculator, https://freecalculator.tech/tools/regex-tester.
Regex Tester — Free Calculator, https://freecalculator.tech/tools/regex-tester