Regex Tester

Test regular expressions and view matching results in real-time.

Regular Expression
/ /
Test String
Highlighted Matches
Matches will be highlighted here...
Match List
Matches will be listed here...
Common Patterns
What is Regex?

Regular expressions (regex) are sequences of characters that define search patterns. They're used for string matching, searching, and text manipulation. Regex is supported in virtually all programming languages and many text editors. While powerful, regex syntax can be complex and requires practice to master.

Regex Syntax Basics

Regex uses literal characters and metacharacters. Common metacharacters include: . (any character), * (zero or more), + (one or more), ? (optional), ^ (start), $ (end), [] (character class), () (grouping), | (alternation). Escape special characters with backslash.

Common Use Cases
  • Validating email addresses and phone numbers
  • Extracting data from text (web scraping)
  • Search and replace in code editors
  • Log file analysis and parsing
  • Input sanitization and validation
Common Patterns
Email ^[\w.-]+@[\w.-]+\.\w+$
URL https?://[\w.-]+(?:/[\w.-]*)*
Phone (US) \d{3}-\d{3}-\d{4}
IPv4 \d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}
Frequently Asked Questions

Why doesn't my regex work in different languages?

Regex flavors vary between implementations. JavaScript, Python, and PCRE have subtle differences in supported features. Always test your regex in the target environment.

How do I make regex more efficient?

Avoid catastrophic backtracking by using specific character classes instead of .*, use anchors (^ and $), and prefer possessive quantifiers when available. Profile complex patterns with large inputs.