Regex Tester & Debugger
Test regular expressions with real-time matching and highlighting. Pattern library included.
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Regular Expression
Test String
Results
Enter a pattern and test string to see results
Why Choose Filator's Regex Tester?
Instant Results
See matches highlighted in real-time as you type. No button clicks needed—results update instantly with every keystroke.
100% Private
Everything runs in your browser. Your regex patterns and test data never leave your device—zero server uploads, zero tracking.
Works Offline
Install as a PWA and use anywhere—airplane, coffee shop, or secure environments. No internet required after first load.
How to Test Regular Expressions Online
Filator's regex tester lets you test and debug regular expressions instantly in your browser. Unlike Regex101 (requires WebAssembly) or RegexTester.com (server-based with ads), Filator processes everything client-side for complete privacy and instant results—with no signup required.
Why Choose Filator's Regex Tester?
⚡ Instant Real-time Testing
Matches highlight immediately as you type—no "Run" button needed. Competitors like FreeFormatter require manual execution, while Regex101 can lag with complex patterns due to WebAssembly overhead.
🔒 Complete Privacy
Your patterns and test strings never leave your browser. Unlike Regex101 which may log patterns for features like "save and share," Filator has zero server communication for testing.
📚 Built-in Pattern Library
Common patterns for email, phone, URL, IP address, dates, and more—ready to use with one click. No hunting through external documentation or Stack Overflow.
🌐 Works Offline
Install as a PWA for offline regex testing. Perfect for secure environments, travel, or when you just need to test patterns without internet—something server-based competitors cannot offer.
How to Test Regex Step-by-Step
- 1.Enter your regex pattern in the pattern field (e.g., \d+ for digits, [a-z]+ for lowercase letters)
- 2.Toggle regex flags as needed: g (global), i (case insensitive), m (multiline), s (dotAll)
- 3.Paste or type your test string in the test area
- 4.See matches highlighted instantly with match count and positions
- 5.View capture groups in the match details section for complex patterns
- 6.Copy your pattern with one click when you're ready to use it
Filator vs Competitor Comparison
| Feature | Filator | Regex101 | RegExr | RegexTester |
|---|---|---|---|---|
| Processing | Client-side | WebAssembly | Client-side | Server-based |
| Signup Required | Never | For saving | For saving | Optional |
| Offline Support | Yes (PWA) | No | No | No |
| Ads | None | Sponsors | Minimal | Google Ads |
| Mobile Optimized | Yes | Partial | No | Partial |
Regex Features Supported
- • Character Classes: \d, \w, \s, [a-z], [^abc] and all standard character class syntax
- • Quantifiers: *, +, ?, {n}, {n,m} for flexible matching
- • Anchors: ^, $, \b, \B for position-based matching
- • Groups: Capturing groups (), non-capturing (?:), and named groups (?<name>)
- • Lookaround: Lookahead (?=) (?!) and lookbehind (?<=) (?<!) assertions
- • Unicode: Full Unicode support with the u flag for international text matching
- • Flags: All JavaScript flags: global (g), case insensitive (i), multiline (m), dotAll (s), unicode (u), sticky (y)
Common Use Cases
📧 Email Validation
Test email regex patterns before implementing in your forms. Validate formats and catch edge cases.
🔍 Log File Analysis
Build patterns to extract timestamps, IP addresses, or error codes from log files and server outputs.
📝 Text Processing
Create search and replace patterns for bulk text transformations in editors, scripts, or applications.
🛡️ Input Validation
Test patterns for phone numbers, credit cards, passwords, and usernames before deploying to production.
Frequently Asked Questions
What is a regex tester and how do I use it?
A regex tester is a tool that lets you test regular expression patterns against sample text to see what matches. Enter your regex pattern in the pattern field, paste your test string, and see matches highlighted instantly. Filator's regex tester shows match positions, capture groups, and named groups in real-time.
Is the regex tester free to use?
Yes, Filator's regex tester is completely free with no signup required. Unlike Regex101 which requires an account to save patterns, Filator works instantly with no registration. There are no usage limits, ads, or premium features locked behind a paywall.
Does the regex tester work offline?
Yes, Filator's regex tester works offline after initial load. It's a Progressive Web App (PWA) that processes everything in your browser. Unlike server-based tools like RegexTester.com that need internet connectivity, Filator works anywhere.
What regex flavors are supported?
Filator uses JavaScript's native RegExp engine, which supports all modern regex features including lookahead, lookbehind, named capture groups, and Unicode properties. This is the same regex flavor used in Node.js, Chrome, Firefox, and modern browsers.
Is my data safe when using the regex tester?
Absolutely. Filator processes everything 100% client-side in your browser. Your regex patterns and test strings never leave your device. Unlike Regex101 or RegExr which may log patterns on their servers, Filator has zero server communication for pattern testing.
How do I test regex with capture groups?
Use parentheses in your pattern to create capture groups, e.g., (\d3)-(\d4) for phone numbers. Filator shows each capture group separately in the match details, including named groups if you use the (?<name>pattern) syntax.
What regex flags are available?
Filator supports all JavaScript regex flags: g (global - match all), i (case insensitive), m (multiline - ^ and $ match line breaks), s (dotAll - . matches newlines), u (unicode), and y (sticky - match from lastIndex). Toggle flags with checkboxes for instant results.
How is Filator different from Regex101?
Filator is simpler, faster, and more private. While Regex101 is feature-rich with 8 regex flavors, it requires WebAssembly and can be slow. Filator focuses on JavaScript regex with instant results, works offline, requires no account, and never sends your data to any server.
Ready to Test Your Regex?
Start testing regular expressions instantly with no signup, complete privacy, and a built-in pattern library. Fast, secure, and works offline—everything you need for regex development without the complexity of Regex101 or the ads of RegexTester.com.