Test regular expressions in real-time with match highlighting, group capture, flag toggles, and a replacement mode for find-and-replace operations.
//g
g (global)i (case-insensitive)m (multiline)s (dotAll)
Matches will be highlighted here.
No matches yet
Result will appear here.
About Regex Tester
The Regex Tester is an interactive developer tool for building, testing, and debugging regular expressions in real-time. Regular expressions (regex) are powerful pattern-matching tools used in programming, data validation, search-and-replace operations, and text processing. Our tester provides instant visual feedback with match highlighting, group capture display, flag toggling, and a replacement mode that shows find-and-replace results. Whether you're validating email addresses, extracting data from logs, or building complex search patterns, our regex tester helps you get it right the first time.
How to Use the Regex Tester
Enter Pattern: Type your regular expression pattern in the input field between the forward slashes. Use the preset buttons for common patterns like email, URL, or IP address matching.
Set Flags: Toggle the regex flags (g for global, i for case-insensitive, m for multiline, s for dotAll) to control matching behavior.
Add Test String: Paste or type your test text in the textarea. Matches are highlighted in real-time as you type.
Review Results: Check the highlighted output for match positions, review captured groups, and use replacement mode for find-and-replace testing.
Features
Real-Time MatchingSee matches highlighted instantly as you type patterns and test strings without clicking any button.
Group CaptureDisplay all captured groups with their index and matched content for complex pattern extraction.
Flag TogglesEnable/disable global, case-insensitive, multiline, and dotAll flags with visual toggle buttons.
Replacement ModeTest find-and-replace patterns with backreferences ($1, $2) to see the transformed output.
Common PresetsOne-click presets for email, URL, IP address, phone number, date, and hex color patterns.
Match StatisticsSee total match count, group count, and processing status for your regex patterns.
Benefits
Regular expressions are notoriously difficult to write and debug. The Regex Tester eliminates trial-and-error by providing instant visual feedback. Instead of running code to test a pattern, you see results in real-time. The highlighted matches show exactly what your pattern captures, the group display reveals extracted data, and the replacement mode validates find-and-replace operations. This saves hours of debugging and helps you write accurate patterns the first time.
Use Cases
Input ValidationBuild and test regex patterns for validating emails, phone numbers, URLs, and other user inputs.
Data ExtractionTest patterns for extracting specific data from logs, text files, API responses, and documents.
Search & ReplaceBuild complex find-and-replace patterns with backreferences for text transformation tasks.
Log AnalysisCreate patterns for parsing server logs, error messages, and structured text data.
Why Use TooliFyra's Regex Tester?
TooliFyra's Regex Tester combines simplicity with power. The real-time highlighting means you see results instantly without any button clicks. The replacement mode with backreference support is rare in browser-based tools. The preset patterns provide starting points for common use cases, and the flag toggles make it easy to experiment with different matching modes. Everything runs in your browser, making it safe for testing patterns against sensitive data.
Frequently Asked Questions
The tool uses JavaScript's native RegExp engine, supporting all standard regex features including character classes, quantifiers, anchors, lookaheads, lookbehinds, backreferences, and named groups. It follows the ECMAScript specification.
In replacement mode, $1 refers to the first captured group, $2 to the second, and so on. $& inserts the entire match. For example, with pattern (\w+)@(\w+) and replacement $2@$domain, "user@email" becomes "email@domain".
Yes, the tester handles long text efficiently. However, extremely complex patterns with catastrophic backtracking on long strings may cause slowdowns. For best performance, be specific with quantifiers and avoid nested optional groups.
Yes, named groups using (?<name>pattern) syntax are supported. The groups display shows both the numeric index and the group name for easy identification of captured data.