Regex Tester - Test Regular Expressions Online
Quickly test and debug your regular expressions with our free online Regex Tester. Paste your pattern and test string to instantly see matches, capture groups, and substitution results. Whether you are validating input, parsing logs, or extracting data, this tool gives you real-time feedback so you can get your regex right the first time.
Features
- Real-time match highlighting that shows every match as you type your pattern
- Capture group inspection with numbered and named group display
- Common pattern library with ready-to-use patterns for emails, URLs, phone numbers, dates, and more
- Flag support for global, case-insensitive, multiline, and dotall modes
- Substitution preview to test find-and-replace operations before running them in code
- Match count and position details showing start and end indices for each match
- Shareable links so you can save and share your regex with teammates
How to Use
- Enter your regular expression in the pattern field at the top of the page.
- Set the desired flags (global, case-insensitive, etc.) using the flag toggles.
- Paste or type your test string in the input area below.
- View highlighted matches in real time. Click any match to see its capture groups.
- Optionally enter a replacement string to preview substitution results.
Use Cases
- Form validation: Test email, phone, or postal code patterns before adding them to your frontend code.
- Log parsing: Build patterns that extract timestamps, error codes, or IP addresses from server logs.
- Data extraction: Write capture groups to pull structured data out of unstructured text files.
- Code refactoring: Preview find-and-replace patterns across your codebase safely.
FAQ
What regex flavor does this tool use?
The Regex Tester uses JavaScript-compatible regular expressions (ECMAScript syntax), which is the same flavor used in most modern browsers and Node.js environments.
Can I test multiline patterns?
Yes. Enable the multiline flag to make ^ and $ match the start and end of each line rather than the entire string. You can also enable the dotall flag so that . matches newline characters.
Is my data stored or shared?
No. All processing happens entirely in your browser. Your test strings and patterns are never sent to a server or stored anywhere.