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TypeScript 6.0 Beta Released: The Last Version Built on JavaScript Before the Go Rewrite

Microsoft released the TypeScript 6.0 beta, the final version of the compiler written in JavaScript, adding ES2025 as the new default target, built-in Temporal API types, and strict mode on by default ahead of the planned Go-based TypeScript 7.0.

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Microsoft released the TypeScript 6.0 beta on February 17, 2026, marking a historically significant moment for the language: this is the final version of the TypeScript compiler and language service to be written in JavaScript. TypeScript 7.0, currently in development, will ship a new compiler implementation written in Go, designed to take advantage of native code performance and shared-memory multi-threading.

The beta is available now via npm install -D typescript@beta, with the stable release planned for March 17, 2026.

Key Features in TypeScript 6.0

ES2025 as the new default target. The compiler now targets ES2025 by default, reflecting the current state of JavaScript engine support across modern runtimes. The design intent is for the default target to track the most recent supported ECMAScript specification version.

Built-in Temporal API types. TypeScript 6.0 ships with native type definitions for the Temporal API, the long-awaited replacement for JavaScript\'s problematic Date object. The Temporal proposal has reached Stage 3 in the TC39 process and is expected to land in JavaScript formally in the near future. Developers can access Temporal types today via --target esnext or by including "esnext" in the lib array.

Strict mode on by default. New TypeScript projects will have strict mode enabled by default, along with module set to esnext. This aligns TypeScript\'s out-of-the-box behavior with the settings that the TypeScript team has long recommended for new codebases.

Looking Ahead to TypeScript 7.0

TypeScript 6.0 clears the slate for the architectural transition ahead. The Go-based compiler in TypeScript 7.0 is expected to deliver substantial improvements in compilation speed, particularly for large codebases where the JavaScript-based compiler has run into performance limits. The TypeScript team has been transparent that the Go rewrite is motivated primarily by the need for native concurrency and lower memory overhead — constraints that the JavaScript runtime cannot overcome.

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