Regular Expression Tester
Test regex with flags and see matches instantly — all in your browser.
Processed in your browser — nothing is sent.
About this tool
The Regex Tester helps you write and check regular expressions with confidence, showing matches instantly against your own sample text. It is built for developers who need to craft patterns for validating data, extracting strings, or finding and replacing — without running real code to trial and error each attempt.
Getting a regex right is tricky, and round-tripping it through your codebase every time is slow. This regex tester removes that friction: type a pattern, paste some text, and the matching parts are highlighted immediately, so you can refine the pattern quickly until it does exactly what you want.
A few things make testing regex easier here:
- Flag support, including g for all matches, i for case-insensitive, and m for multiline
- Live results that update as you type
- Direct testing against your real text, with no environment to set up
Because the tool runs in the browser, it uses JavaScript regular expression syntax, which closely matches most other languages. All testing happens locally on your device — both the pattern and the sample text are never sent anywhere. It is free, needs no account, and lets you test without limits.
How to use
- 1Type the regular expression you want to test into the pattern field
- 2Add flags such as g, i, or m to adjust how matching behaves
- 3Paste your sample text into the test area
- 4See the matches highlighted in the text instantly
- 5Tweak the pattern and watch the result update until it is right
Frequently asked questions
- What is a regular expression?
- A regular expression, or regex, is a pattern used to search and match text by rules — finding emails, phone numbers, or words that fit a shape. It works in almost every programming language.
- What do flags like g, i, and m do?
- g matches every occurrence rather than just the first, i ignores case, and m makes the anchors work across multiple lines. Pick the ones your task needs.
- Does this use the same regex as JavaScript?
- Yes. Because it runs in the browser it uses JavaScript regex syntax, which is close to other languages, though some advanced features can differ slightly.
- Is my test data sent to a server?
- No. All testing happens in your browser, and your pattern and sample text are never sent anywhere.
- Is it free, and do I need to sign up?
- It is completely free with no signup, and you can test as much as you like.