TypeScript Announced — Microsoft

TypeScript is a programming language from Microsoft that adds optional static types to JavaScript and compiles to ordinary JavaScript. It was announced on 1 October 2012, when Microsoft released an early preview, version 0.8, together with the language specification, the compiler's source code and a Visual Studio plug-in. Its best-known figure is Anders Hejlsberg, the lead architect of C#, who introduced the language at launch and signs himself as TypeScript's lead architect. The stable release, TypeScript 1.0, followed on 2 April 2014. In August 2025 GitHub counted TypeScript as the most used language on its platform by monthly contributors, ahead of Python and JavaScript.

The problem: JavaScript at application scale

The launch post on S. Somasegar's MSDN blog framed TypeScript as a language that "solves a very specific problem – getting JavaScript development to scale". JavaScript engines had grown fast — the post notes that JavaScript speed had doubled every nine months over the previous five years by the SunSpider benchmark — and the language had spread beyond the browser into Windows 8 apps and Node.js on servers. Applications "of unprecedented size" were being written in a language that had begun as event handlers scripting a web page, and it lacked the means to state contracts between components.

Teams had been patching the gap with outside tools: Script# for static typing, JSLint for checking, Google's Closure Compiler for explicit contracts, and conventions such as the module pattern. TypeScript set out to put those in the language itself. In Somasegar's definition, "TypeScript is a superset of JavaScript that combines type checking and static analysis, explicit interfaces, and best practices into a single language and compiler."

1 October 2012: the design

Three choices defined TypeScript from the first day.

The output was meant to run on any browser, host or operating system and to plug into the existing JavaScript toolchain. Declaration files — "a thin shim of type information" in the post's words — let developers describe existing libraries such as jQuery and the DOM without changing them. The mechanism caught on quickly: the 1.0 announcement eighteen months later reported that the community had already written hundreds of type definition files.

The language specification was released under the Open Web Foundation's Final Specification Agreement (OWFa 1.0), and the compiler was published on CodePlex, with git, under the Apache 2.0 licence. Tooling was the other half of the pitch: a TypeScript for Visual Studio 2012 plug-in brought code navigation, refactoring, static error messages and IntelliSense — the experience of statically typed languages — to JavaScript. TechCrunch's report that day quoted Hejlsberg's argument that the language would make it easier to build larger applications.

2014: TypeScript 1.0

TypeScript 1.0 arrived on 2 April 2014, about eighteen months after the 0.8 preview. The announcement made it available through Visual Studio 2013, npm and source code, described it as a first-class citizen of Visual Studio, and said the team was beginning to accept pull requests from the community. It reported real-world TypeScript codebases already exceeding half a million lines.

From preview to GitHub's top language

GitHub's Octoverse 2025 report, published on 28 October 2025, said that "By GitHub contributor counts, August 2025 marks the first time TypeScript emerged as the most used language on GitHub, surpassing Python by ~42k contributors". It also observed that nearly every major front-end framework now scaffolds new projects with TypeScript by default.

2025–26: rewriting the compiler in Go

For most of its life the TypeScript compiler was itself written in TypeScript. On 11 March 2025 Hejlsberg announced a native port to Go, promising that it would "drastically improve editor startup, reduce most build times by 10x, and substantially reduce memory usage". The JavaScript-based compiler would continue as TypeScript 6.x, and the native one would become TypeScript 7. On 8 July 2026 Microsoft announced the availability of TypeScript 7, which it described as a 10x faster native port; the announcement reports full-build speedups of 7.7x to 11.9x across major open-source projects. A language created to make JavaScript scale had reached the point where its own compiler needed a faster language underneath.

TypeScript sits on the programming-languages timeline after its parent, JavaScript, and among Microsoft's developer tools on the Microsoft timeline. What a type system checks is explained under type system.