TypeScript 7 and Project Corsa: Everything You Need to Know About the 10x Faster Go Rewrite

In March 2025, Anders Hejlsberg sat in front of a camera and said something nobody expected: "We are porting the TypeScript compiler to Go." Not Rust. Not a gradual rewrite. A full port of the TypeScript compiler, language service, and type checker — the very heart of the TypeScript ecosystem — from TypeScript to Go. Microsoft called it Project Corsa , and it's now shipping as TypeScript 7.0 . The numbers are staggering. The VS Code codebase — 1.5 million lines of TypeScript — compiles in about 78 seconds with tsc today. With the new Go-based compiler, tsgo , it takes 7.5 seconds . That's not a 2x improvement. That's 10.4x . This isn't minor tooling drama. It's the biggest change in TypeScript's 12-year history, and it has profound implications for how we build, ship, and think about TypeScript. Let's break down everything you need to know. Why a Rewrite? Why Now? To understand Project Corsa, you need to understand what was breaking. TypeScript's original compiler was written in TypeSc