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Format minified JSON with readable indentation.
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Regex Tester
Test regular expressions and inspect every match. Your input stays in this browser during processing.
Private local processing
Your text and settings stays in this browser.
About Regex Tester
Test a JavaScript-flavor regular expression against sample text and see every match with its number and character offset.
What the result contains
Every regular-expression match with its match number and character offset.
Accepted input
- PLAIN
- TXT
How to use Regex Tester
- Enter your regular expression and any flags, such as g or i.
- Paste the sample text to test it against.
- Review each match, its number and its position.
- Adjust the pattern and re-test until the matches look correct.
Practical example
Test an email-like pattern against sample lines using g and i flags.
Check your result before using it
Test both strings that should match and strings that should not. Include an empty input, punctuation, non-ASCII text and a long near-match when these are realistic cases. Check flags and the boundaries of each highlighted match before copying the expression. A pattern that succeeds on one example can still match too broadly, and browser JavaScript regular expressions may differ from the engine used in your destination application.
When to use Regex Tester
- Test an email-matching pattern against a list of sample lines
- Debug why a regular expression isn't matching expected text
- Check a pattern's matches before using it in application code
Important limitations
- The tool uses the browser's JavaScript regular-expression syntax.
- Catastrophic backtracking patterns can freeze a page; test complex expressions on short, non-sensitive samples.
Troubleshooting Regex Tester
A pattern works elsewhere but fails here
Compare regex flavors and replace features unsupported by JavaScript, such as engine-specific flags or syntax.
Private local processing
The text and settings is processed on this device and is not uploaded to MyFileNest. Closing or refreshing the page clears the active session.
Frequently asked questions
Practical limit: Large text or structured-data inputs can respond more slowly in the browser. Verify generated output before using it in a production workflow.