Regex Tester

About Regex Tester

Regular expressions are powerful but tricky. Enter a pattern, flags and test text and the tool highlights every match and counts them, with errors shown if the pattern is invalid. It uses JavaScript regex rules. Use it to build and debug patterns for validation and search.

Example

Input: pattern \b\w+@\w+\.\w+\b on a text with two email addresses. Output: two matches highlighted.

Tips for better results

• Start simple and build up.
• Remember that patterns differ between languages.
• Test with both matching and non-matching examples.

When to use Regex Tester

Use this when you need a pattern for matching, extracting or checking text and want to see results immediately instead of running code repeatedly. Developers write form validation, log parsing and search-and-replace rules with it. Marketers and analysts use it to clean exported lists or build filters in tools that accept patterns. Testing against several sample lines first helps you catch a pattern that matches too much or too little.

Real-world uses

• A developer builds a pattern to check that a phone number field contains only digits, spaces and dashes before a form is submitted.
• An SEO specialist writes a pattern to match old URL paths with a numeric ID so they can plan redirect rules in a site tool.
• A support analyst pulls order numbers out of a pasted block of customer emails by testing a pattern against the whole text.
• A student learning regular expressions types small patterns and watches which parts of a sentence light up to understand how quantifiers behave.

Common mistakes to avoid

• Forgetting to escape special characters such as a period, plus sign or parenthesis when you mean the literal character. A bare period matches almost anything.
• Writing a greedy pattern that grabs far more than intended, for example matching from the first quote to the last quote on a line instead of each pair.
• Using a pattern from the tool in another language without checking that language's syntax, especially for named groups, lookbehinds and flags.

Test regular expressions with live match highlighting. It works instantly in your browser, so there is nothing to install and nothing to upload. Regex Tester is part of our collection of 100 free tools in the Developer & Data category.

How to use it

1. Enter your information or choose a file in the tool above.
2. Your result appears right below the tool.
3. Copy the result, or adjust your input and try again.

Frequently asked questions

Why does my pattern match only once?

Without the global flag, a JavaScript pattern stops after the first match. Turn on the g flag to find every match in the text and see them all highlighted.

How do I match across multiple lines?

The caret and dollar sign match line starts and ends only when the multiline flag is on. To let a period cross line breaks, use the s flag or a character class such as [\s\S].

Is Regex Tester free to use?

Yes. Regex Tester is completely free and you do not need to create an account.

Is my data uploaded anywhere?

No. This tool runs in your browser, so what you type or choose stays on your device.

How accurate are the results?

Calculations use standard formulas, but always double-check important figures, especially for money, health or legal decisions.