Regex Tester

A live regex playground in your browser

The Regex Tester lets you build a regular expression and watch it match against your own sample text in real time. It is handy for developers writing validation rules, anyone scraping or cleaning data, and people who just want to confirm a pattern catches the right strings before pasting it into code. Because it runs on the browser’s native JavaScript engine, the matches you see here are the same ones your app will get.

How to use the Regex Tester

1. Paste or type the text you want to search into the large input box.
2. In the Pattern field, enter your regular expression, for example \b\w+@\w+\.\w+\b to find email-like strings.
3. In the Flags field, add the flags you need such as i for case-insensitive or m for multiline. The default is g.
4. Read the output: it lists how many matches were found, each matched substring with the index where it starts, and any capture group values.
5. Tweak the pattern and flags until the matches look right, then copy your expression into your project.

Why test your regex here

It is fast, free, and there is no sign-up. Nothing you paste leaves your machine, which matters when your sample text contains logs, emails, or other private data. The result updates as you type, so you can iterate quickly instead of re-running a script. If your pattern is broken, you get a clear “Invalid regex” message explaining what went wrong rather than a silent failure.

A quick tip

Start broad and narrow down: write a loose pattern first, confirm it catches your targets, then tighten it with anchors like ^, $, or \b to cut false positives. Add capture groups with parentheses when you want to pull pieces out of each match, and the tool will show you exactly what each group grabbed.