Regex Tester

Test and debug regular expressions with live pattern matching and highlighting.

Test patterns live

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About This Tool

Test and debug regular expressions with live pattern matching. See matches highlighted in real-time as you type. Supports JavaScript regex syntax with all common flags. All processing happens locally in your browser.

About

About the Regex Tester

A Regex Tester lets you write a regular expression, run it against sample text, and see exactly what it matches in real time. It's the fastest way to build, debug, and verify a pattern before you drop it into your code, validation rules, or find-and-replace. Everything runs entirely in your browser, so the patterns and text you test never leave your device.

How to use the Regex Tester

  1. 1Type or paste your regular expression into the pattern field.
  2. 2Set any flags you need, such as global, case-insensitive, or multiline.
  3. 3Paste the sample text you want to test the pattern against.
  4. 4Watch matches highlight live as you edit the pattern or the text.
  5. 5Refine the expression until it captures exactly what you intend, then copy it into your project.

Common use cases

  • Validating input formats like emails, phone numbers, URLs, or postal codes before writing the validation rule into your app.
  • Debugging a pattern that isn't matching what you expect by testing it against real sample data.
  • Building search-and-replace expressions for editors, log processing, or bulk text edits.
  • Learning regex syntax interactively by seeing matches update as you tweak the pattern.
  • Extracting structured data such as dates, IDs, or tokens from unstructured text.

Frequently asked questions

What is a regex tester?

It's a tool that runs a regular expression against sample text and shows you which parts match. It's used to build and debug patterns interactively instead of guessing whether they work in your code.

Is my data private and safe?

Yes. The tool runs entirely in your browser. Your pattern and test text are processed locally and never uploaded, stored, or tracked, so it's safe for sensitive or proprietary content.

Is this regex tester free to use?

Yes, it's completely free with no sign-up required. You can test as many patterns and inputs as you like.

What regex syntax does it support?

It tests JavaScript-style regular expressions as evaluated by your browser, including common flags like global, case-insensitive, and multiline. Engine-specific features from other languages such as PCRE, Python, or .NET may behave differently, so verify edge cases in your target environment.

Why does my pattern match more or less than I expect?

Common causes are a missing global flag (only the first match shows), unescaped special characters like . or *, or greedy quantifiers grabbing too much. Adjust the flags or escape literal characters and the live highlighting will confirm the fix.

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