Form Validation Tester
Test form validation rules for email, phone, password and custom regex patterns before you ship. Free online form validation tester for developers.
About Regex Validator
The Doffl regex validator helps developers, QA testers, and analysts test and debug regular expressions in real time. Validate complex form input patterns, such as email addresses, phone numbers, and custom alphanumeric strings, before deploying them into production code.
Because this tool runs entirely in your browser, your test strings and validation data remain private on your device without being sent to external servers. It is free to use with no installation or account creation required.
Key features
- Real-time regex syntax checking and match detection
- Pre-built pattern examples for emails, URLs, and phone numbers
- Client-side execution ensuring input data remains secure
- Support for standard JavaScript regular expression flags
- Instant error reporting for invalid or broken syntax
- Clean test interface with capture group breakdowns
How to use Regex Validator
- Enter or paste your regular expression into the pattern field.
- Select your desired matching flags such as global, multiline, or case-insensitive.
- Paste your target text or sample form input into the test area.
- Review matching substrings and capture groups highlighted in real time.
- Adjust your pattern as needed until validation passes all test cases.
Who is it for?
- Frontend developers testing email and password validation rules for web forms
- QA engineers verifying pattern edge cases before approving release builds
- Backend engineers creating regex filters for data sanitization and parsing
- Data analysts extracting specific phone, date, or ID formats from text files
Frequently asked questions
Is this regex validator free to use?
Yes, the tool is completely free to use with no account or subscription required.
Does this regex tool send my data to a server?
No, all pattern matching and text evaluations run directly in your browser. Your test strings and data never leave your local device.
Which regex flavor does this validator support?
It uses JavaScript's native ECMAScript regular expression engine, which supports standard flags like g (global), i (case-insensitive), and m (multiline).
Can I test form validation patterns like emails or URLs?
Yes, you can test any standard form input regex, including common patterns for email addresses, URLs, zip codes, and phone numbers.
What happens if my regular expression contains a syntax error?
The validator detects syntax mistakes instantly and displays a clear error message explaining the problem so you can fix your pattern immediately.