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Regex Tester

Test and debug regular expressions live

Flags:
Common Patterns
No matches

What is Regex?

Regex (short for Regular Expressions) is a powerful syntax for describing search patterns in text. With regular expressions, you can search, validate, and replace strings based on specific patterns. Regex is supported in virtually every programming language and is an indispensable tool for developers, system administrators, and data analysts. Typical use cases include validating email addresses, extracting URLs from text, or searching through log files. Mastering regex can dramatically improve your text processing productivity.

How do I use the Regex Tester?

Enter your regular expression in the pattern field and the text to search in the test text field. Matches are highlighted live as you type. You can enable the flags Global (g), Case-insensitive (i), and Multiline (m) via checkboxes. In the match details section, you can see all individual matches including group contents and their position in the text. In replace mode, you can specify a replacement text and see the result live. Use the pre-built patterns for common use cases like email, URL, or phone numbers.

Why test Regex online?

Developing and debugging regular expressions can be complex. Our online tester gives you immediate visual feedback, so you can spot errors faster than in an IDE or terminal. All computations run directly in your browser. No data is transmitted to any server. The JavaScript RegExp engine is used, so the results are directly applicable to your JavaScript and TypeScript projects without any compatibility concerns.

More Tools

Also try our Regex Generator to build patterns visually, the Diff Checker to compare results, or the JSON Formatter for structured data.

Frequently Asked Questions

Which regex engine is used?
The browser's native JavaScript RegExp engine is used, so behavior matches what you'll see in JS/TS projects.
Are PCRE features like lookbehind supported?
Modern browsers support lookbehind in JavaScript. Other PCRE-only features like recursion are not available.
Can I test replace operations?
Yes, in replace mode you enter a replacement string (with $1, $2 backreferences) and see the result live.
Is my test text sent to a server?
No, all matching happens in your browser. Even sensitive log data stays private.

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