TypeScript 6.0 Beta Marks the End of an Era as Microsoft Prepares Go-Based Compiler That Builds 10x Faster
TypeScript 6.0 beta is the last version built on JavaScript. The Go-based TypeScript 7.0 promises 10x faster builds.
Overview
Microsoft released the TypeScript 6.0 beta on February 11, marking a watershed moment for one of the most widely used programming languages in the world. This release is the final version of TypeScript built on its original JavaScript codebase — a self-hosted architecture that has defined the language since its creation more than a decade ago. TypeScript 7.0, already available as a developer preview under the codename Project Corsa, will replace the JavaScript compiler entirely with a native implementation written in Go that delivers build speeds up to 10 times faster, according to Microsoft’s TypeScript team.
What’s New in TypeScript 6.0
Despite its transitional role, TypeScript 6.0 ships with substantial new features and some of the most aggressive breaking changes in the language’s history, according to the official announcement.
ES2025 and the Temporal API. The release introduces es2025 as a compilation target and library option. This brings built-in type definitions for RegExp.escape(), the ECMAScript Temporal API for modern date and time handling, and new “upsert” methods on Map and WeakMap — getOrInsert() and getOrInsertComputed() — that eliminate a common pattern of checking for key existence before inserting a value.
Strict by default. The strict flag now defaults to true, a change the TypeScript team says reflects industry best practices. The default compilation target has also shifted from older settings to es2025, and the default module system is now esnext.
Legacy removal. TypeScript 6.0 drops support for ES5 as a compilation target entirely, making ES2015 the minimum. The --outFile option has been removed, and module formats amd, umd, and systemjs are no longer supported. The --moduleResolution classic and node (Node10) strategies are deprecated, as is --baseUrl for module resolution. The types field in tsconfig.json now defaults to an empty array rather than auto-including all @types packages.
Improved type inference. Functions that do not reference this are no longer treated as contextually sensitive, allowing the type checker to process them earlier and produce better inference results. Support for Node.js subpath imports using the #/ prefix is also now available under node20, nodenext, and bundler module resolution modes.
Bridging to TypeScript 7.0
The most forward-looking addition is the --stableTypeOrdering flag, which aligns the current compiler’s output with the deterministic type ordering behavior of the upcoming Go-based compiler. Microsoft cautions that enabling the flag can slow type checking by up to 25 percent, but recommends it for teams planning early migration to TypeScript 7.0.
The Go-based compiler, known internally as tsgo, is already available as a preview through npm install -g @typescript/native-preview. According to Microsoft, its language service is “largely stable and available for daily use,” powering IDE features like code completion and refactoring in Visual Studio Code.
Performance gains from the rewrite are dramatic. The VSCode codebase — roughly 1.5 million lines of TypeScript — compiles in 8.74 seconds with tsgo compared to 89 seconds with the current JavaScript-based tsc, a 10.2x speedup. Across large repositories, Microsoft reports full-build speedups generally in the 7x to 10x range, as noted in the original native port announcement.
Microsoft chose Go over alternatives like Rust, C, and C++ for the rewrite, citing Go’s automatic garbage collection and its functional programming style, which the team found aligned well with the existing codebase architecture.
What We Don’t Know
The JavaScript-based codebase will continue to be maintained in the 6.x line until TypeScript 7.0 reaches sufficient maturity and adoption. Microsoft has not announced a firm release date for TypeScript 7.0’s stable release, though the preview has been available since late 2025.
The transition also raises unresolved questions for the ecosystem. Developers who depend on the TypeScript compiler API — including maintainers of build tools, transformers, and refactoring utilities — have expressed concerns about compatibility with the new Go-based AST handling and LanguageService interface. How smoothly tens of thousands of existing TypeScript projects migrate to the new compiler remains to be seen.
Timeline
TypeScript 6.0 is on track for a release candidate on February 24 and a stable release on March 17, 2026. The ignoreDeprecations: "6.0" setting is available to temporarily suppress warnings for deprecated features, giving teams time to update their configurations before the removals become permanent in TypeScript 7.0.