Regex Tester
About Regex Tester
Write, test, and debug regular expressions with real-time match highlighting against your own test string. Every match is highlighted inline, capture groups are listed separately so you can inspect what each group captured, and all standard flags (g, i, m, s, u, y) are supported. Ideal for building form validators, search filters, log parsers, and replacement patterns — paste your pattern, paste your test text, and see matches the moment you type. Everything runs in your browser.
How To Use
- Enter your regular expression in the pattern field and pick any flags (g, i, m, s, u, y).
- Paste or type your test string into the input area.
- Read the highlighted matches and the captured groups to confirm your pattern behaves as expected.
Example
Input: The pattern \b\w+@\w+\.\w+\b tested against a list of email-like strings.
Output: Every email-shaped substring highlighted, with the local-part and domain captured as groups.
Who Uses Regex Tester
- Developers who prefer private, browser-only tools for formatting, validation, and data work.
- Engineers who need fast local tools without installing anything or uploading code.
- Teams that want private — files and text stay on your device and are never uploaded to a server.
Frequently Asked Questions
Which regex flags can I use?
All standard JavaScript flags are supported: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode), and y (sticky). Toggle them on the pattern input.
Does it show capture groups?
Yes. When your pattern contains parentheses, each capture group is listed alongside the overall match so you can see exactly what each group extracted.
What regex flavor does it use?
JavaScript (ECMAScript) regular expressions, which cover the vast majority of everyday patterns used on the web.
Is my input uploaded anywhere?
No. Matching happens entirely in your browser, so you can safely test patterns against real data such as log lines or form input.