Why TypeScript 6.0 Beta Switches to Go: Faster Builds and Lower Memory

Microsoft recently announced the TypeScript 6.0 beta, which will be the final release of the language written in JavaScript. Starting in 2025 the team is rewriting the native implementation of TypeScript in Go to improve editor startup time, reduce build time, and lower memory consumption.

TypeScript chief architect Anders Hejlsberg explained that the JavaScript‑based implementation, while offering many benefits, has long caused performance and scalability challenges because the JavaScript runtime is optimized for UI and browser workloads rather than the compute‑intensive tasks of a compiler.

Product manager Daniel Rosenwasser added in a blog post that moving the compiler to Go allows the project to take advantage of native code speed and shared‑memory multithreading.

The team says TypeScript 6.0 will serve as a bridge between the current 5.9 release and the upcoming 7.0 version, laying the groundwork for future features.

Several compiler defaults have changed in this preview: strict defaults to

true

module

defaults to

esnext

target

defaults to the current year’s ECMAScript version noUncheckedSideEffectImports defaults to

true

libReplacement

defaults to false In addition, the tsconfig.json handling has been updated: the default rootDir is now the directory containing the configuration file rather than being inferred from the common ancestor of all non‑declaration input files.