Free Regex Tester
Test JavaScript regular expressions, highlight matches, inspect match details and check regex flags instantly in your browser.
Last Updated: August 2026
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Your text and regular expressions are processed locally in your browser.
What Is a Regex Tester?
A Regex Tester helps you experiment with regular expressions and check how a pattern matches text. Regular expressions, commonly called regex, are used in programming, data processing, validation, search operations and text manipulation.
Testing a pattern with representative sample text can make it easier to find unexpected matches or missing cases before using the expression in a project.
How to Test a Regular Expression
- Enter your JavaScript regular expression.
- Select the flags you need.
- Enter sample text.
- Click Test Regex.
- Review the total matches, highlights and match details.
- Adjust the pattern and test again if necessary.
Common Regex Flags
| Flag | Name | Purpose |
|---|---|---|
| g | Global | Find all matches instead of stopping after the first. |
| i | Ignore Case | Match letters without treating uppercase and lowercase as different. |
| m | Multiline | Changes how ^ and $ behave across multiple lines. |
| s | Dot All | Allows the dot character to match newline characters. |
Common Uses for Regular Expressions
- Find text patterns in documents or source code.
- Validate input formats.
- Extract information from logs and datasets.
- Search and replace text using pattern rules.
- Process structured strings in JavaScript applications.
- Test a pattern before adding it to a project.
Important Regex Testing Tips
- Test normal, edge-case and unexpected input.
- Use the global flag when inspecting multiple matches.
- Remember regex behavior can differ between languages and engines.
- Test the final pattern in the environment where it will be used.
- Keep complex expressions readable and documented when necessary.
Frequently Asked Questions
A Regex Tester is a tool for testing regular expression patterns against sample text and inspecting the matches they produce.
This tool tests JavaScript regular expressions using the browser's built-in JavaScript RegExp engine.
The g flag finds all matches, i ignores case, m enables multiline behavior, and s allows the dot to match newline characters.
No. The regex pattern and test text are processed locally in your browser.
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