What is a Regex Tester?
Regular Expressions (often abbreviated as Regex or RegExp) are powerful search patterns used to match, locate, and manipulate text. Their syntax can be notoriously dense and difficult to debug without real-time feedback.
This regex tester lets you write a pattern and immediately evaluate it against a test string, right in your browser. The instant visual highlighting makes it easy to build and refine complex patterns until they capture exactly what you need — nothing more, nothing less.
How to Use It
Everything runs on the client side, so it's fast and safe even with sensitive text.
- Enter your pattern: Type your regular expression in the top left input field (between the forward slashes).
- Set your flags: In the smaller box after the trailing slash, enter your flags. Common ones:
g(global),i(case-insensitive),m(multiline). - Paste your test text: Put the target data into the "Test String" area.
- Review matches: All matches are highlighted instantly, and any capture groups are extracted into a clean list in the right-hand panel.
Frequently Asked Questions
What is a regex tester?
A regex tester is a browser-based tool that lets developers write, test, and debug Regular Expressions against sample text in real-time. It highlights matches visually, making it much easier to verify that a pattern behaves correctly before deploying it in code.
How do I test a regular expression?
Paste your sample text into the "Test String" box, type your pattern into the Regex field, and apply any flags you need (like g for global or i for case-insensitive). Matches and capture groups are displayed instantly in the results panel.
What are capture groups in regex?
Capture groups are sections of a pattern enclosed in parentheses () that extract specific sub-strings from a match. This tool automatically lists the contents of each group separately, so you can inspect exactly what was captured without digging through the full match string.