Regex Tester

Test regular expressions against any string with live highlighting.

Regular Expression
/ /
Quick patterns:
Test String
Quick Reference
. Any character except newline
* 0 or more
+ 1 or more
? 0 or 1 (optional)
^ Start of string
$ End of string
\d Any digit [0-9]
\w Word character [a-zA-Z0-9_]
\s Whitespace
\b Word boundary
[abc] Character class
(abc) Capture group
a|b a or b
{n,m} Between n and m times
Tips
  • Use the "g" flag to find all matches, not just the first one.
  • The "i" flag makes the regex case insensitive.
  • Capture groups () let you extract specific parts of a match.

What is Regex Tester?

A regex tester is an online tool that lets you write, test, and debug regular expressions (regex) against sample text in real time. It instantly highlights matches, captures groups, and explains what your pattern is doing — eliminating the need to run code just to verify a regex pattern works as intended.
Regular expressions are sequences of characters that define a search pattern. They are used in virtually every programming language — Python, JavaScript, PHP, Java, and Go—for tasks like form validation, text parsing, data extraction, and string manipulation. An online regex tester gives you an interactive sandbox to build and refine your patterns safely before deploying them in your code.

How to Use Regex Tester

1
Open Our Online Regex Tester
Go to a regex tester tool in your browser. Most are free, require no login, and work instantly.
2
Select Your Regex Flavor
Choose the language or regex engine that matches your project — JavaScript, Python, PCRE (PHP/Perl), Java, .NET, Go, or Ruby. Regex syntax and supported features differ between flavors.
3
Enter Your Regular Expression
Type or paste your regex pattern into the expression field. Example pattern to match email addresses
4
Set Your Flags (Modifiers)
5
Paste Your Test String
6
Review the Matches
The tool instantly highlights all matches. Review full matches, capture groups, named groups, and match positions (start and end index).
7
Iterate and Refine
Adjust your pattern based on what matched and what didn't. Good regex testers update highlighting in real time with every keystroke, letting you iterate rapidly.
8
Copy the Final Regex
Once your pattern works correctly on your test cases, copy it directly into your code

Why Use Regex Tester?

Regex testing online offers a faster, smarter alternative to testing patterns directly inside your codebase:
• Instant feedback: See matches highlighted in real time as you type your pattern, no need to save and run a script.
• Zero setup: Open a browser, paste your pattern and text, and start testing immediately — no IDE or dependencies needed.
• Visual match highlighting: Matched portions of your test string are color-highlighted, making it easy to see exactly what your pattern captures.
• Group & capture visualization: See individual capture groups, named groups, and backreferences displayed clearly.
• Flavor support: Test regex in JavaScript, Python, PHP (PCRE), Java, Go, and more — since syntax varies across languages.
• Error detection: Invalid regex syntax is flagged immediately with an explanation, saving you from cryptic runtime errors.
• Learning tool: Invaluable for beginners learning to read and write regular expressions by seeing what each part of a pattern does.

Frequently Asked Questions

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