What is Regex Builder?
Regex Builder is a free online tool for visually constructing and testing regular expressions. It provides live match highlighting with color-coded capture groups, a common patterns library for quick insertion, and detailed match breakdowns. Unlike basic regex testers, this builder helps you construct patterns step by step with visual feedback.
Common Use Cases
Pattern Development
Build complex regex patterns incrementally with instant visual feedback on matches and capture groups.
Data Extraction
Craft regex patterns to extract specific data like emails, URLs, dates, or phone numbers from text.
Input Validation
Design and test validation patterns for form fields, API inputs, and configuration values.
Log Analysis
Create patterns to parse and extract structured data from log files and server output.
How to Use This Tool
- Enter your regex pattern in the input field (without delimiters)
- Toggle regex flags (g, i, m, s, u) as needed
- Paste or type your test string in the text area below
- View highlighted matches and capture group details in real-time
- Use the quick patterns bar to insert common patterns like email or URL
- Copy match results as JSON for use in your code
Frequently Asked Questions
How is this different from the Regex Tester?
The Regex Builder focuses on construction with visual capture group highlighting, a patterns library for quick insertion, and detailed match breakdowns. The Regex Tester is simpler, focused on quick validation.
What regex flags are supported?
All standard JavaScript regex flags: g (global), i (case insensitive), m (multiline), s (dotAll), and u (unicode).
Is my data secure?
Yes! All regex processing happens entirely in your browser using the native RegExp engine. No data is sent to any server.
Can I use named capture groups?
Yes, named capture groups like (?<name>pattern) are fully supported and will appear in the match details panel.