What's New in TypeScript 6.0

TypeScript 6.0 is not a typical feature release. If you upgrade expecting new syntax or dramatic type system changes, you’ll be surprised. This release is primarily about modernizing defaults, removing legacy baggage, and preparing the ecosystem for TypeScript 7.0 — the upcoming native port of the compiler and tooling in Go. Understanding what changed and why will save you hours of debugging after upgrading.

TypeScript 6.0 Is a Bridge Release, Not a Feature Drop

TypeScript 6.0 is intentionally positioned as the last version built on the JavaScript codebase. TypeScript 7.0 is expected to be the native Go-based successor, with much faster builds and editor performance. TypeScript 6.0 cleans up the foundation before that transition happens.

The practical implication: most TypeScript 6.0 changes are about configuration defaults and deprecations, not new language features. If your project has been accumulating legacy tsconfig options, now is the time to address them.

What’s New in TypeScript 6.0: Platform Alignment Features

Despite the transition focus, TypeScript 6.0 does add meaningful support for modern JavaScript APIs.

ES2025 Target and New Built-in Types

TypeScript 6.0 adds es2025 as a valid --target and --lib value. That includes built-in types for APIs like RegExp.escape, and also moves some declarations from esnext into es2025.

It also adds built-in types for newer APIs that are still exposed through esnext:

• RegExp.escape — safely escapes special regex characters in a string
• Temporal API — a modern replacement for Date, typed under esnext or temporal.esnext
• Map.getOrInsert and Map.getOrInsertComputed — cleaner upsert patterns for Map and WeakMap, available through esnext

// Before: verbose Map upsert pattern
if (!map.has("key")) map.set("key", defaultValue)
const value = map.get("key")

// After: clean and concise
const value = map.getOrInsert("key", defaultValue)

DOM Types Consolidation

dom.iterable and dom.asynciterable are now merged into the base dom lib. You no longer need to list them separately in your tsconfig.json. If you were using "lib": ["dom", "dom.iterable"], you can simplify to just "lib": ["dom"].

Subpath Imports Starting with #/

TypeScript now supports Node.js subpath imports using the #/ prefix. That maps cleanly to the imports field in package.json, and makes the feature feel much closer to the alias patterns bundler users are already familiar with.

TypeScript 6.0 Breaking Changes: What Will Actually Break Your Project

This is where most of the TypeScript 6.0 migration effort lives. Several compiler defaults have changed.

The types: [] change is one of the most impactful. Previously, TypeScript auto-included every package in node_modules/@types. Now it includes nothing by default. Projects that rely on globals from @types/node, @types/jest, or similar packages will see errors like:

Cannot find name 'process'. Try adding 'node' to the types field in your tsconfig.

Fix it explicitly:

{
  "compilerOptions": {
    "types": ["node", "jest"]
  }
}

The rootDir change is also common. If your output files suddenly appear at dist/src/index.js instead of dist/index.js, add "rootDir": "./src" to your tsconfig.

Another change worth watching is noUncheckedSideEffectImports: true. If your codebase has side-effect-only imports with typos or shaky resolution, TypeScript 6.0 is more likely to flag them.

TypeScript 6.0 Deprecations: What to Remove Before TypeScript 7

These options are deprecated in 6.0 for the TypeScript 7.0 transition, and a few older behaviors are already gone:

• --target es5 (the lowest supported target is now ES2015)
• --moduleResolution node / --moduleResolution classic → migrate to nodenext or bundler
• --module amd, umd, systemjs, none
• --baseUrl → move the prefix into your paths entries directly
• --outFile → use a bundler like esbuild, Vite, or Rollup
• esModuleInterop: false and allowSyntheticDefaultImports: false
• Legacy module Foo {} namespace syntax → use namespace Foo {}
• Import assert syntax → replace with with

You can silence deprecation warnings temporarily with "ignoreDeprecations": "6.0" in your tsconfig, but that should be treated as a short-term stopgap.

Upgrading to TypeScript 6.0

Install the current 6.0 release candidate with:

npm install -D typescript@rc

Run tsc --noEmit and work through the errors. Most issues will stem from the types array, rootDir, side-effect imports, and deprecated options.

Conclusion

TypeScript 6.0 is a cleanup release, not a feature showcase. Its purpose is to retire legacy defaults, align the compiler with modern JavaScript, and prepare the ground for the native TypeScript 7.0 line. The sooner you address these migration changes — updated types arrays, explicit rootDir values, side-effect import issues, and deprecated option replacements — the smoother your path to TypeScript 7.0 will be.

If you want the full technical breakdown from the TypeScript team, you can also read the official TypeScript 6.0 RC announcement.

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