The highly anticipated TypeScript 6.0 was released today, bringing a suite of updates focused on modernization, performance, and crucial preparation for the future of the language. If you are a developer working within the JavaScript and TypeScript ecosystem, this update marks an important transitional milestone.

In this post, we'll dive into the main TypeScript 6 features and what changes in your daily development workflow.

1. New Default Compiler Options

The TypeScript 6 update introduces significant changes to default configurations, enforcing stricter standards out of the box:

Strict Mode Enabled: The strict option now defaults to true. New projects will be strictly typed unless explicitly opted out.
Modernized Target: The default target has been updated from ES3 to ES2025, matching the latest ECMAScript standards.
Module Resolution: The module option now natively resolves to es2022 or esnext.

2. Module System Clean-up

Say goodbye to legacy module support. TypeScript 6 has removed built-in support for AMD and UMD modules. The compiler will now emit errors if you attempt to use them, pushing the ecosystem toward ESM (ECMAScript Modules) best practices.

3. Enhanced Type Inference and Control Flow

TypeScript 6.0 delivers more accurate type narrowing in complex control flow scenarios and discriminated unions. Smarter recursive type resolution and improvements to Template Literal Types have also been introduced to aid advanced pattern-typing.

4. Bridging to the Go-Based Compiler (TypeScript 7.0)

One of the biggest TypeScript 6 updates isn't just about what it brings today, but what it sets up for tomorrow. This is widely considered the final JavaScript-based major release. The performance improvements included now are a taste of what's to come in TypeScript 7.0, which will feature a completely new engine built in Go for massive, multi-threaded performance gains.

How to Prepare Your TypeScript 6 Migration

When upgrading, be sure to review your tsconfig.json, check for any deprecated module systems, and expect slightly stricter type-checking. To temporarily silence deprecation warnings, you can utilize the new ignoreDeprecations flag.