RegEx Tester
Test regular expressions with real-time matching, capture groups, and replace functionality
Enter a regex pattern and test text to get started!
Supports all JavaScript regex features and flags
Enter your regular expression pattern in the 'Regular Expression Pattern' field using standard JavaScript regex syntax. The tool supports the complete range of regex metacharacters, quantifiers, character classes, anchors, and advanced features like lookaheads, lookbehinds, and non-capturing groups. Patterns are processed in real-time as you type, providing immediate feedback on syntax validity.
Configure regex flags to control pattern matching behavior using the flag toggles. Global flag enables finding all matches in text, ignore case makes matching case-insensitive, multiline allows ^ and $ to match line boundaries, dotAll makes . match newlines, unicode enables full Unicode support, and sticky restricts matches to start at the last match position. Multiple flags can be combined for complex matching requirements.
Input your test text in the 'Test Text' area, which can contain single lines, multiline content, mixed character sets, special characters, or any text format you need to process. The tool handles large text blocks efficiently and preserves all formatting, whitespace, and Unicode characters for accurate pattern testing against real-world data.
Review the current pattern display that shows your complete regex with active flags in standard notation (e.g., /pattern/gim). This visual confirmation helps ensure your pattern and flags are configured correctly before testing and provides a reference for copying patterns to your development environment.
Analyze match results in the statistics summary showing the total number of matches found. Successful matches are highlighted with a success badge, while zero matches display a secondary badge, providing immediate visual feedback on pattern effectiveness without scrolling through results.
Examine highlighted text display where all matches are visually emphasized with colored highlighting against the original text context. This visual representation makes it easy to verify that your pattern is matching the intended text portions and helps identify unexpected matches or missed content.
Explore detailed match information in the expandable match details section, which provides comprehensive data for each match including the exact matched text, character position range, capture group values, and named group assignments. Each match is individually copyable for integration into your applications or documentation.
Use the copy functionality to transfer individual matches, all matches combined, or the complete pattern with flags to your clipboard for immediate use in code editors, documentation, or other regex tools. The clear button resets all inputs for testing new patterns from a clean state.
Pro Tips
- Start with simple patterns and gradually add complexity to avoid overwhelming regex syntax errors. Test basic character matching first, then add quantifiers, groups, and advanced features incrementally to isolate issues and understand how each component affects matching behavior.
- Use the global flag consistently when you need to find all occurrences of a pattern in text, not just the first match. This is crucial for data extraction, text replacement operations, and comprehensive text analysis where missing matches could compromise results.
- Leverage capture groups to extract specific portions of matched text for data processing. Regular parentheses create numbered groups (accessed via \1, \2), while named groups (?<name>pattern) create labeled captures that are easier to reference and maintain in complex patterns.
- Test your patterns with edge cases including empty strings, single characters, very long text, mixed character encodings, and boundary conditions like start/end of lines. Real-world text often contains unexpected formatting that can break poorly tested patterns.
- Use the ignore case flag judiciously - while convenient for user input validation, it can cause unexpected matches in data processing scenarios where case sensitivity matters for accurate parsing or classification.
- Optimize patterns for performance by placing commonly matching alternatives first in alternation groups (pattern1|pattern2), using non-capturing groups (?:pattern) when you don't need to extract the content, and avoiding excessive backtracking with greedy quantifiers in complex patterns.
- Document complex patterns by testing them thoroughly and using the match details to understand exactly what each group captures. This documentation becomes invaluable when maintaining or modifying patterns months later.
Why Use This Tool?
The Regex Tester provides essential pattern development capabilities that streamline text processing workflows and ensure regex accuracy across professional applications and development projects.
- Real-time pattern validation and testing eliminates the guesswork from regex development, providing immediate feedback on pattern syntax, matching behavior, and edge cases before implementation in production code
- Comprehensive flag support enables precise control over matching behavior with global, case-insensitive, multiline, dotAll, Unicode, and sticky options for handling diverse text processing requirements
- Advanced capture group analysis with detailed match breakdown showing exact positions, group values, and named group assignments for effective data extraction and pattern debugging
- Visual match highlighting provides intuitive pattern verification by clearly showing which text portions match your pattern, making it easy to identify unintended matches or missed content
- Professional debugging features including error reporting, pattern syntax validation, and detailed match statistics help identify and resolve pattern issues quickly during development
- Developer-friendly interface with one-click copying of patterns, matches, and results for seamless integration into code editors, documentation, and development workflows
- Cross-platform JavaScript regex compatibility ensures patterns developed and tested in this tool work consistently across web browsers, Node.js, and other JavaScript environments
- Educational value for learning regex syntax and behavior through interactive testing, making it valuable for skill development and training in text processing techniques