Regex Tester

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

1. Enter your regular expression and any flags, such as g or i.
2. Paste the sample text to test it against.
3. Review each match, its number and its position.
4. Adjust the pattern and re-test until the matches look correct.

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

Private local processing

The text and settings are processed on this device and are 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.