Regex Tester

Report an Issue

Help us improve by telling us what went wrong.

Embed this Tool

Customize and copy the embed code for your website.

Regular expressions are one of those skills that separate productive developers from the rest. They are incredibly powerful for pattern matching, validation, and text extraction - but they are also notoriously difficult to write correctly on the first try. That is exactly why a dedicated Regex Tester is an essential part of any developer's toolkit.

Test Patterns with Instant Visual Feedback

This regex tester lets you type a regular expression pattern and immediately see which parts of your test string match. Matches are highlighted in real time as you type, so you can iteratively refine your pattern without the tedious cycle of writing code, running it, checking the output, and going back to edit. That feedback loop - which might take thirty seconds in a code editor - happens instantly here.

You can test against single-line strings or multi-line blocks of text. The tool supports all standard JavaScript regex flags including global (g), case-insensitive (i), multiline (m), dotAll (s), and Unicode (u). Toggle them on or off and watch the matches update immediately.

Capture Groups and Match Details

Beyond simple match highlighting, the tester breaks down capture groups for each match. If your pattern contains parenthesised groups, you will see exactly what each group captured - numbered groups and named groups alike. This is invaluable when you are building patterns for data extraction, such as pulling dates, email addresses, or structured identifiers out of unstructured text.

The match details panel shows the full match string, its position (start and end index) within the test text, and every group's content. For complex patterns with multiple groups, this level of visibility can save significant debugging time.

Common Regex Tasks This Tool Handles

Email validation is one of the most searched-for regex patterns on the internet, and for good reason - getting it right is tricky. Use this tester to paste a candidate pattern and throw edge cases at it: addresses with plus signs, subdomains, new TLDs, and the various formats that technically comply with RFC 5322.

URL parsing patterns need to handle protocols, subdomains, paths, query strings, and fragments. Testing against a dozen real-world URLs in this tool reveals gaps in your pattern that you would never catch by eyeballing the regex alone.

Log file analysis often involves writing patterns to extract timestamps, error codes, IP addresses, or user agents from server logs. Paste a sample log block into the test area and refine your pattern until every line highlights correctly.

Data cleaning - stripping unwanted characters, normalising phone numbers, extracting numbers from mixed text - all of these tasks become straightforward when you can see your regex matches updating live as you adjust the pattern.

Why Developers Prefer a Browser-Based Regex Tester

IDE plugins and command-line tools can test regex, but a browser-based tool has distinct advantages. It requires zero setup - no extensions to install, no terminal commands to remember. It works on any device with a browser, including tablets and Chromebooks. And because this particular tester runs entirely client-side, your test data never leaves your machine. You can safely test patterns against sensitive log data, customer records, or proprietary content without any privacy concerns.

Learning Regex? Start Here.

If you are still learning regular expressions, there is no better way to build understanding than interactive experimentation. Type a simple pattern like \d+ and watch it highlight all numbers in your text. Then try \b\w{5}\b to match exactly five-letter words. Gradually increase complexity and observe how each metacharacter, quantifier, and grouping construct changes the match results. The instant feedback makes abstract concepts concrete in a way that reading documentation alone never can.

Bookmark this regex tester and reach for it whenever you need to write, debug, or understand a regular expression. It is one of those tools that pays for itself - in time saved - every single week.