Regex Tester
Test and debug regular expressions with real-time matching.
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What is Regex Tester?
A regex (regular expression) tester allows you to test and debug your regular expression patterns against sample text in real-time. It shows all matches, capture groups, and match positions instantly. Regular expressions are powerful patterns used in programming for searching, matching, and manipulating text.
How to Use This Tool
- Enter your regular expression pattern in the pattern field
- Set flags (g, i, m, s) as needed for your use case
- Paste or type test text in the text area
- View matches instantly with group information
Common Use Cases
- Validating user input formats (emails, phones, dates)
- Extracting data from log files and text
- Search and replace operations in text editors
- Building form validation patterns
Frequently Asked Questions
What do the flags g, i, m, s mean?
g (global) finds all matches, i (case insensitive) ignores case, m (multiline) makes ^ and $ match line starts/ends, s (dotall) makes . match newlines too.
How do capture groups work?
Capture groups, defined with parentheses (), extract specific parts of a match. For example, (\d{4})-(\d{2})-(\d{2}) captures year, month, and day separately from a date.
Why isn't my regex matching?
Common issues include forgetting the global flag (g) for multiple matches, not escaping special characters like . or $, or case sensitivity when the i flag is not set.