Regex Tester
Test regex patterns in real-time with match highlighting, group display, and pattern explanation.
Regex Tester
No matches found
No capture groups
Enter a regex pattern to see explanation
Replace result will appear here
What is Regex Tester?
Regex Tester is an online tool that lets you test and debug regular expressions in real-time. You can create complex patterns and see results instantly, significantly improving your development efficiency.
It provides all the features you need for regex work: match result highlighting, capture group inspection, pattern explanation, and string replacement.
Key Features
- Real-time Matching – Match results are highlighted instantly as you type
- Flag Options – Supports g (global), i (case insensitive), m (multiline), s (dotAll), u (unicode)
- Capture Group Inspection – View detailed contents of captured groups
- Pattern Explanation – Auto-analysis of what each regex token means
- String Replacement – Replace matched parts with other strings and see results
- Sample Templates – Common patterns for email, phone, URL, and more
How to Use
- Enter the pattern you want to test in the regex pattern input field
- Select the flags you need (g, i, m, s, u)
- Enter the text you want to test in the test string area
- Matching parts are highlighted in real-time
- Check detailed match results, groups, and pattern explanation in the tabs below
- If replacement is needed, enter the replacement string and click the Replace button
Flag Descriptions
- g (global) – Find all matches instead of stopping at the first match
- i (ignoreCase) – Search without case sensitivity
- m (multiline) – ^ and $ match the start/end of each line
- s (dotAll) – . (dot) also matches newline characters
- u (unicode) – Enables Unicode escape sequence support
Who Is This For?
- Web Developers – Testing form input validation patterns
- Backend Engineers – Creating log parsing and data extraction patterns
- Data Analysts – Text data cleaning and extraction
- QA Engineers – Pattern matching verification for test data
- Students Learning Regex – Learning with real-time feedback
Frequently Asked Questions
How do I match special characters in regex?
Escape special characters by placing a backslash (\) before them. For example, use \. to search for a period (.) and \? to search for a question mark (?).
How do I use capture groups?
Surround a pattern with parentheses () to create a capture group. You can reference them with $1, $2, etc. during replacement. Example: Match with (\\d+)-(\\d+) and replace with $2-$1 to swap the order.
What are lookahead and lookbehind?
Lookahead (?=) finds positions where a specific pattern follows, and lookbehind (?<=) finds positions where a specific pattern precedes. They are not included in the matched string.
What’s the difference between greedy and lazy matching?
Greedy matching (*, +) matches as much as possible, while lazy matching (*?, +?) matches as little as possible. Example: <.+> matches the entire <a><b>, but <.+?> matches only <a>.