What is Regex?

Regular expressions (regex or regexp) are patterns that describe sets of strings. They are used in every programming language for searching, matching, and manipulating text. Common uses include form validation (checking if an email address is valid), data extraction (finding all phone numbers in a document), find-and-replace (changing date formats across a codebase), and input sanitization (removing unwanted characters). Regex syntax uses special characters like . (any character), * (zero or more), + (one or more), [] (character sets), and () (groups) to define patterns. While the syntax can be intimidating, most developers only need a handful of common patterns.