TypeScript is a high-level, open-source programming language developed by Microsoft, first released in 2012. Anders Hejlsberg, also the creator of C#, played a key role in its design. TypeScript is a superset of JavaScript, meaning that all valid JavaScript code is also valid TypeScript code. TypeScript adds static typing with optional type annotations to JavaScript, improving maintainability and scalability in large projects.
TypeScript code is not directly understood by browsers; it is transpiled into plain JavaScript, ensuring compatibility with all web environments. The TypeScript compiler, written in TypeScript, can target specific ECMAScript versions for broader compatibility. TypeScript is used in major tech companies like Google (Angular), Microsoft (VS Code, Teams, Outlook), Airbnb, Uber, Slack, and Facebook. As of December 2025, the latest stable version is 5.9, with version 6.0 in beta. The TypeScript team is working on a Go port of the compiler, expected to be released as TypeScript version 7.0, promising a significant speed improvement. TypeScript 6.0 is intended to be the last release based on the current JavaScript codebase.