Regex Tester

What is the Regex Tester?

The Regex Tester lets you test a JavaScript regular expression against sample text in your browser. A regular expression, or regex, is a pattern that describes text to find, such as digits, words, email addresses, or dates. You enter a pattern, choose flags, enter test text, and the tool lists the matches it finds.

How to Use the Regex Tester

1. Open the Regex Tester page.
2. Enter your pattern in the Regular Expression field, for example \d+ for one or more digits. Do not include the slashes.
3. Set the Flags field, for example g for global, and tick Global, Case Insensitive, or Multiline as needed.
4. Paste your test text into the main workspace box labelled Paste your code here, and also into the Test String field.
5. Click Process and read the matches in the Result panel.

Worked Example

Observed run: pattern \d+, flags g, test text Order 123 shipped on 2024-05-06 returned Pattern: /\d+/g Matches: 4 followed by the matches 123, 2024, 05, and 06. The pattern matched 4 digit groups because \d+ groups consecutive digits together, so 2024 counts as one match, not four.

Limitations

• You must paste the test text twice: once in the main workspace box and once in the Test String field. Using the Test String field alone produced no result in testing.
• The tool uses the JavaScript regex engine only. Patterns written for Python, PCRE, or .NET may behave differently.
• The result lists matched text but does not show match positions or capture-group breakdowns.
• There is no pattern explainer, replacement mode, or multi-line test list observed in the workspace.
• An invalid pattern may produce no result with no clear error message, so test small patterns first.

Frequently Asked Questions

Which regex flavour does this tool use?

JavaScript. That is the same engine used by browsers and Node.js, so \d, \w, \s, character classes, and quantifiers behave as in JavaScript.

What does the g flag do?

It finds all matches instead of stopping at the first one. Without g, the example above would return only 123.

Why did Process show no result?

Most often the test text was only in the Test String field. Paste the same text into the main workspace box as well, then click Process again.

Can I test case-insensitive matching?

Yes. Add i to the Flags field or tick Case Insensitive. For example, apple with i matches Apple and APPLE.