TypeScript 7 Arrives: The Go-Rewritten Compiler That Ships 10x Faster Builds

TypeScript 7.0 shipped on July 8, 2026 — and it is not a normal point release. For the first time in the project's history, the compiler you run is no longer written in TypeScript. Microsoft has replaced the 12-year-old, self-hosted compiler with a native one written in Go. The language is unchanged; the command is still tsc; the npm package is still typescript. What changed is the engine underneath — and it compiles most codebases about ten times faster.

Why Microsoft rewrote the compiler

The project's lead architect, Anders Hejlsberg, planted the flag in a March 2025 post bluntly titled A 10x Faster TypeScript. The story is one of scale. TypeScript's codebase solved huge problems, but it ran on a JavaScript runtime — a platform tuned for UI and browsers, not for compute-heavy jobs like compilers. As projects grew into millions of lines, developers hit slow builds and, increasingly, out-of-memory crashes.

A port, not a rewrite, was the goal. The team moved the existing compiler function by function from TypeScript to Go, deliberately preserving logic and file order so every quirk of the type checker carries over. No new semantics, no new language — just the same behavior running far faster. Internally the effort was called Project Corsa.

Where the 10x comes from

Roughly half the speedup is from running natively. Go compiles to optimized machine code and gives full control over data layout, with garbage collection and good support for concurrency. The rest comes from parallelism. Parsing, binding, and emit are "embarrassingly parallel" — independent files are handled across cores. The checker, which must reason across files, is split across a small pool of parallel type checkers.

The headline numbers from the announcement are vivid: the VS Code codebase (about 1.5 million lines) went from 77.8 seconds to 7.5 seconds; TypeORM from 17.5 to 1.3 seconds — a 13.5x drop. The native language service also cut editor project load from ~9.6 seconds to ~1.2 seconds. In real-world releases since, Microsoft reports 8x–12x build improvements across codebases.

From preview to stable

The compiler first reached developers as an npm preview package, @typescript/native-preview, exposing a tsgo command alongside tsc. It became extraordinarily popular for unreleased tooling — over 8.5 million downloads a week — before the Go port moved into the mainline compiler, reached release candidate in June 2026, and landed as TypeScript 7.0.

What it means for you

If you upgrade to TypeScript 7, your code should behave the same — the compiler caught the same errors during its long preview period. The notable changes are defaults: some options that TypeScript 6 deprecated have been removed, and new defaults lean on the faster engine. One honest caveat: the stable programmatic API is not yet final (expected in 7.1), so low-level tooling that drives the compiler programmatically may want to wait. And not every project got the full 10x in early testing, but the order-of-magnitude improvement is real for most codebases.

A compiler rewrite this deep is rare. That TypeScript managed it while keeping source compatibility is a masterclass in careful engineering — the same kind of discipline that keeps a chess engine fast as its rules stay fixed.