Regex Tester

A regex tester is used to test and debug regular expression patterns before using them in code. It allows you to verify that your pattern matches the intended text, visualize matches, debug errors, and understand capture groups. This tool provides real-time feedback, highlighting matches as you type, making it essential for developers working with pattern matching, data validation, and text extraction.

To test a regular expression: 1) Enter your regex pattern in the pattern field, 2) Paste or type your test text, 3) Configure flags (case-insensitive, global, multiline), 4) View real-time matches highlighted in the results. The tool shows match positions, capture groups, and the total number of matches. You can also upload text files for testing and export results.

Regex flags modify pattern matching behavior. The 'i' flag (case-insensitive) ignores letter case in matches. The 'g' flag (global) finds all matches instead of just the first one. The 'm' flag (multiline) makes ^ and $ match line starts/ends instead of string starts/ends. Simply check or uncheck the flag options in the tool to enable them.

Capture groups use parentheses ( ) to extract specific parts of a match. For example, in the pattern '(\d3)-(\d2)-(\d4)' for a SSN, each set of parentheses captures a portion. Our tool displays all capture groups for each match, showing you exactly what each group extracted. This is useful for parsing structured data and extracting specific information.

The regex replace feature allows you to not only find matches but also replace them with different text. You can use capture groups in the replacement text with $1, $2, etc. This is useful for reformatting data, cleaning text, or transforming strings. Our tool shows you the replacement results in real-time as you type.

Click the 'Pattern Library' tab to access common regex patterns including email addresses, phone numbers, URLs, IP addresses, credit cards, dates, hex colors, and social security numbers. Each pattern includes a description and example. Click 'Use' to load any pattern directly into the tester for immediate use or customization.

Click the 'Cheat Sheet' tab to view a comprehensive regex reference. It covers character classes (\d, \w, \s), quantifiers (*, +, ?, {n,m}), anchors (^, $, \b), groups, and special characters. Each symbol includes a clear description. Use this reference while building your patterns in the Test tab.

Yes! All regex testing happens entirely in your browser using JavaScript. Your patterns and test text are never uploaded to our servers or transmitted anywhere. The tool works completely offline after loading, ensuring your sensitive data remains private and secure on your device.