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Test your regular expressions (regex) online with instant live match highlighting. See which parts of your text match your pattern, view capture groups, toggle flags (global, case-insensitive, multiline), and catch syntax errors before using regex in your code.
Test regular expressions with live match highlighting
Enter a regex pattern and test string to see results
What is a Regex Tester?
A regex tester is an online tool that helps you test and debug regular expression patterns before using them in your code. It lets you type a regex pattern, paste some test text, and immediately see what matches, what doesn't match, and whether your pattern has any syntax errors.
Regular expressions (regex for short) are patterns used to search, match, and manipulate text. They're used everywhere in programming — validating email addresses, extracting phone numbers, parsing log files, cleaning up text, and way more. But regex can be tricky. One wrong character and your pattern might match nothing at all, or match way more than you expected.
That's where a regex tester comes in. Instead of guessing whether your pattern works, you can test it right here in the browser. Type your pattern, see matches highlighted in real time, view capture groups, toggle flags like case-insensitive or global search, and catch errors before you ship your code. No more debugging regex in production.
Why Use a Regex Tester?
Don't guess whether your regex works. See exactly what matches in real time as you type. Matches are highlighted in the test string so you know your pattern is correct before you use it.
Regex syntax errors can break your code. This tester catches them immediately and shows you exactly what's wrong. Fix errors here instead of debugging in production.
See what your capture groups extract. Whether you're using numbered groups, named groups, or backreferences, you'll see exactly what each group captures from every match.
Regex flags change how patterns match. Toggle global, case-insensitive, multiline, dotAll, unicode, and sticky flags to see how they affect your results instantly.
Stop wasting time writing test code to check your regex. Test patterns here in seconds instead of writing scripts, running tests, and debugging why matches don't work.
See how regex patterns work in real time. Experiment with character classes, quantifiers, anchors, and lookaheads. Instant feedback helps you learn faster than reading docs alone.
How It Works
This regex tester runs entirely in your browser using JavaScript's built-in regular expression engine. Nothing is uploaded to a server — your patterns and test strings stay private on your device.
When you type a regex pattern, the tester creates a JavaScript RegExp object with the flags you selected. It then runs that pattern against your test string using match and exec methods. Every match is highlighted in the test string with clear visual indicators. If your pattern has capture groups, they're extracted and displayed separately so you can see exactly what each group captures.
If there's a syntax error in your regex pattern, the JavaScript engine throws an error. The tester catches that error and shows you a clear message explaining what went wrong. This prevents crashes and helps you fix issues fast.
All processing happens instantly as you type — no clicking calculate buttons or waiting for results. It's designed to be fast, accurate, and helpful for developers testing regex in JavaScript, though the syntax is similar across most programming languages.
Type your regular expression pattern in the regex input field. You can use all standard regex syntax — character classes, quantifiers, anchors, groups, lookaheads, and more.
Paste or type the text you want to test against your pattern. Can be a single line, multiple lines, or even an entire document. The tester handles any length.
Click flag buttons to enable global (g), case-insensitive (i), multiline (m), or other flags. Watch results update instantly as you toggle flags on and off.
See all matches highlighted in your test string. Check the results panel to view match details, capture group values, and match counts. Fix your pattern if needed and test again.
Features
See matches highlighted in real time as you type your regex pattern. Instantly know what matches and what doesn't without clicking any buttons.
View all capture groups extracted from your matches. See group 0, group 1, group 2, and named groups with clear labels and values.
Toggle global (g), case-insensitive (i), multiline (m), dotAll (s), unicode (u), and sticky (y) flags to test different matching behaviors instantly.
Catch regex syntax errors immediately with clear error messages. Know exactly what's wrong with your pattern before you use it in code.
See how many matches your regex finds. Track total matches, position indexes, and match lengths for every result.
Start fast with built-in presets for emails, phone numbers, URLs, dates, numbers, and more. Click to load and customize instantly.
Test regex against large blocks of text. Works perfectly with multiline strings, paragraphs, log files, and code snippets.
Clean, distraction-free interface designed for developers. Monospace fonts, syntax colors, and keyboard-friendly controls.
Use Cases
Test regex patterns for validating email addresses. Make sure your pattern matches valid emails and rejects invalid formats before using it in forms or APIs.
Test patterns that extract or validate phone numbers. Handle different formats like (555) 123-4567, 555-123-4567, or international numbers with country codes.
Validate and extract URLs from text. Test patterns that match HTTP, HTTPS, FTP links and extract protocol, domain, path, query params, and fragments.
Test regex for matching date formats like MM/DD/YYYY, YYYY-MM-DD, or natural dates. Validate user input or parse dates from logs and documents.
Extract function names, variable declarations, or comments from code. Test patterns for syntax highlighting, linting, or building development tools.
Test regex patterns that enforce password rules — minimum length, required uppercase, lowercase, numbers, special characters. Verify rules work as expected.
Tutorial
Follow this step-by-step guide to test your regular expressions effectively and catch issues before using regex in your code.
Type your regex pattern in the pattern input field, or click one of the preset buttons (Email, Phone, URL, etc.) to load a common pattern as a starting point. You can edit any preset to fit your needs.
Paste or type text into the test string field. Use real examples that your regex needs to match or reject. The more realistic your test data, the more confident you'll be that your pattern works correctly.
As you type, matches are highlighted instantly in the test string. Green highlights show what your regex matched. If nothing highlights, your pattern might be too strict or have a syntax error.
Click flag buttons to enable global (g) for all matches, case-insensitive (i) to ignore uppercase/lowercase, multiline (m) for line-by-line matching, and others. See how flags change your results.
If your pattern uses parentheses for capture groups, check the groups panel. You'll see group 0 (full match), group 1, group 2, and so on. Named groups show with their custom names.
If you see a syntax error message, read it carefully — it tells you what's wrong. Fix the error and test again. Keep tweaking your pattern until it matches exactly what you need and nothing extra.
Once your pattern works perfectly, copy it from the tester and paste it into your JavaScript, Python, Java, PHP, or other code. Remember to include the flags you used during testing.
FAQs
Regex (regular expressions) are patterns used to search and match text. You use them to validate emails, extract phone numbers, parse logs, clean up text, and more. Testing regex before using it in code prevents bugs and saves time debugging.
Comparison
This regex tester is simple, fast, and free. Here's how it compares to writing test code or using other tools.
You need to test regex in a specific language flavor (Perl, .NET, Python with specific modules)
Recommendation: Use language-specific testers or IDE plugins that match your exact regex engine.
You want to save and organize dozens of regex patterns for reuse
Recommendation: Use a tool with account-based pattern libraries, or store patterns in your own code repository or snippet manager.
You're debugging extremely complex regex and need step-by-step execution visualization
Recommendation: Use advanced debuggers like Regex101's debugger mode or RegexBuddy for detailed step-through analysis.
You just need quick testing with instant results and no setup
Recommendation: This tool is perfect. Load, test, and go in seconds without sign-up or clutter.
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Start testing regular expressions now. See live matches, view capture groups, toggle flags, and catch errors instantly — all free, no sign-up required.
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