Test and debug regular expressions with our interactive RegEx tester. Real-time matching, syntax highlighting, and visual feedback. Perfect for developers.
Capture groups are parts of your regex pattern inside parentheses that let you extract specific matches. For example, with the email pattern:
Each set of parentheses ( ) creates a numbered group, which you can use to extract parts of the match.
A comprehensive guide to understanding and using regular expressions
Metacharacters are the building blocks of regular expressions that have special meaning. They allow you to define patterns beyond literal text matching, enabling powerful search and validation capabilities.
Matches any single character except newline. Useful for matching patterns where any character is acceptable.
Control how many times a pattern can match.
*
Zero or more occurrences+
One or more occurrences?
Zero or one occurrence (optional)When you need precise control over the number of occurrences, exact quantifiers let you specify exact counts or ranges. These are particularly useful for matching structured data like phone numbers, dates, or any pattern with a known length.
Match exactly n occurrences of a pattern.
Match between n and m occurrences.
Match at least n occurrences.
Groups allow you to treat multiple characters as a single unit and capture parts of the match. Assertions let you add conditions to your matches without including them in the result.
Group patterns together and capture the matched text.
Match patterns only if followed or preceded by another pattern.
These are frequently used regex patterns for common validation tasks like emails, phone numbers, and dates. These patterns have been tested and optimized for real-world use cases.
Basic email format validation that covers most common email patterns.
Matches common US phone number formats with optional country code.
Matches common date formats including MM/DD/YYYY and YYYY-MM-DD.
Matches valid URLs with optional protocol and subdomains.
Validates password with minimum requirements: 8+ chars, uppercase, lowercase, number, special char.
Our RegEx tester helps you build and test regular expressions in real-time. See matches instantly, test against your own text, and use common patterns to get started quickly. All processing happens in your browser for maximum privacy and speed.
A regular expression is a sequence of characters that defines a search pattern. It's commonly used for string matching, validation, and text manipulation.
Flags modify how the regex pattern matches. Common flags include 'g' (global), 'i' (case-insensitive), 'm' (multiline), and 's' (dot matches newlines).
Capture groups are parts of a regex pattern enclosed in parentheses that let you extract specific portions of the matched text. They're useful for complex pattern matching and text extraction.
Lookahead (?=) and lookbehind (?<=) are zero-width assertions that match a pattern without including it in the result. They're useful for pattern matching with specific conditions.
Yes, all pattern matching happens directly in your browser. No data is sent to any server or stored anywhere.
Our regex decoder helps you understand complex patterns by breaking them down into parts. For example, '^[0-9]+$' can be decoded as: '^' (start of line), '[0-9]' (any digit), '+' (one or more times), '$' (end of line). Use our tester to visualize how each part of the pattern matches.
To match digits in regex, you can use '[0-9]' or '\d'. For example, '\d+' matches one or more digits, '\d{3}' matches exactly three digits, and '\d*' matches zero or more digits. Our tool includes common patterns for numbers, making it easy to validate numeric input.
Phone number patterns vary by format and region. A common US phone regex is '\(?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}', which matches formats like (123) 456-7890, 123.456.7890, or 123-456-7890. You can customize this pattern in our tester for different formats or international numbers.