Regex tester
Test a regular expression against text as you work.
Regex Tester
Test your regular expressions against sample text. See all matches instantly with support for common regex flags. Perfect for debugging and validating patterns.
How It Works
Enter your regex pattern and optional flags
Paste the text you want to test against
Review the matches as they update
Features
Frequently Asked Questions
Is this tool really free?
Yes, 100% free with no hidden costs or limits. All processing happens.
Do I need an account?
No. The tool is free to use with no sign-up, no watermark and no limits.
What regex flags are supported?
We support g (global), i (case-insensitive), m (multiline), s (dotAll), and u (unicode) flags.
Regex Tester Online, The Complete Guide
Test regex online with our free regular expression tester. Validate patterns, match text, and debug regex online in real-time, essential for developers working with text processing and validation.
Regex Validator Free
Our regex validator free tool checks your pattern syntax instantly. See errors highlighted as you type, with explanations of what went wrong. No more guessing why your regex does not work.
Regex Pattern Matcher
The regex pattern matcher highlights all matches in your test string. See exactly what your regex captures, including groups. Color-coded highlighting shows matched portions clearly.
Regex Checker with Flags
Our regex checker supports all standard flags: global (g), case-insensitive (i), multiline (m), dotAll (s), and unicode (u). Toggle flags to see how they affect your pattern matching.
Tips for Working with Regex
- Start simple and build complexity gradually
- Use capturing groups () to extract specific parts
- Test with edge cases including empty strings
- All processing happens locally, your data stays private
Related Tools
More than a quick regex tester.
A regex tester lets you see how a regular expression matches a sample string before you put it into a form, validation rule, search, or codebase. Immediate feedback makes it easier to spot a pattern that is too broad, too narrow, or syntactically invalid.
Test with realistic examples, including values that should fail. A pattern that matches one happy path may still accept incorrect input or reject valid content in the real application.
How to use the regex tester.
Start with the tool above. There is no account step between you and the result.
- 01
Enter the pattern and choose flags.
- 02
Paste a representative test string.
- 03
Review the updated matches and test both valid and invalid cases.
Regex tester answers.
Useful context before you use the result somewhere important.
What do regex flags do?
Flags change how matching behaves. For example, global finds multiple matches and case-insensitive ignores letter case.
Why is my pattern invalid?
A bracket, escape, group, or flag may be malformed. Simplify the pattern and add pieces back carefully.
Should I test negative cases?
Yes. Test text that should not match as well as text that should.
Give the document a place to go.
Keep PDFs, templates, feedback, approvals and signatures together in one workspace.