Regex Tester
All articles about regex tester — tips, tutorials, and practical guides.
Regular Expressions for Beginners
A gentle introduction to regex — what it is, why it matters, and how to start.
Regex Syntax: A Complete Reference
Every regex metacharacter, quantifier, and special sequence explained.
Character Classes in Regex: [a-z], \d, \w Explained
Understanding character classes for matching specific types of characters.
Quantifiers in Regex: *, +, ?, {n,m}
How quantifiers control repetition and matching behavior in regex.
Capture Groups and Backreferences
Using parentheses to capture and reference matched text in regex.
Lookahead and Lookbehind Assertions
Advanced zero-width assertions for context-dependent matching.
Regex Flags: g, i, m, s, u Explained
Understanding regex flags and how they modify pattern behavior.
Common Regex Patterns: A Reference Library
A curated collection of regex patterns for emails, URLs, dates, and more.
Regex for Email Validation
Building and understanding regex patterns for email address validation.
Regex for URL Matching and Extraction
Patterns for matching URLs in text with various protocols and formats.
Regex for Phone Number Validation
Creating flexible phone number patterns for different international formats.
Regex for Data Extraction from Text
Techniques for pulling structured data out of unstructured text.
Regex in JavaScript: Methods and Best Practices
Using regex with match, replace, test, and exec in JavaScript.
Regex Performance: Avoiding Catastrophic Backtracking
Understanding and preventing regex patterns that cause performance issues.
Regex for Log File Analysis
Parsing and extracting data from server logs with regular expressions.
Regex for HTML Parsing: Possibilities and Limits
What regex can and cannot do when working with HTML content.
Regex for Password Validation
Building regex patterns that enforce password complexity requirements.
Non-Greedy vs Greedy Matching in Regex
Understanding the difference between greedy and lazy quantifiers.
Named Capture Groups in Modern Regex
Using named groups for more readable and maintainable regex patterns.
Regex in Different Programming Languages
How regex syntax and features vary across JavaScript, Python, Java, and C#.
Regex for CSV and Structured Data
Using regex to parse and validate structured data formats.
Testing Regex Patterns: Methodology and Tools
Systematic approaches to building and testing regex patterns.
Regex for Natural Language Processing
How NLP applications use regex for tokenization and text analysis.
Alternation and Grouping in Regex
Using the pipe operator and groups for complex pattern matching.
Regex for Text Transformation and Cleanup
Combining regex with replacement for powerful text transformations.
Anchors in Regex: ^, $, \b Explained
Understanding position anchors for matching at specific text locations.
Regex for IP Address and Network Validation
Patterns for matching IPv4, IPv6, and CIDR notation.
Debugging Regex: Common Mistakes and Fixes
Troubleshooting guide for the most common regex errors.
The History and Theory of Regular Expressions
From mathematical theory to practical programming tool — the regex story.
FreeTextForge Regex Tester: Live Testing Guide
A complete walkthrough of the FreeTextForge Regex Tester's features.