Regex Cheat Sheet with Examples: A Complete Developer Reference

Regular expressions are one of the most powerful and most misunderstood tools in a developer's toolkit. They look intimidating, they're hard to read after the fact, and the syntax varies subtly between languages. But mastering the core patterns unlocks a capability you'll use constantly—pattern matching, validation, extraction, and transformation across text. This is the regex cheat sheet you'll actually bookmark: complete coverage of the syntax, real examples for each concept, and the common patterns you'll copy-paste into production code. Test any pattern from this guide in the DevPlaybook regex playground —real-time highlighting, group visualization, and pattern explanation built in. Core Concepts What Regex Matches A regular expression is a sequence of characters that defines a search pattern. When you apply a regex to a string, the engine scans the string looking for substrings that match the pattern. Most characters in a regex match themselves literally. cat matches the sequence