TypeScript 6.0: new compiler and features

# TypeScript 6.0: Transition to the New Compiler and Key Improvements

Microsoft released TypeScript 6.0 on March 23, 2026. This version serves as a bridge between 5.9 and the upcoming 7.0, where the typescript-go compiler on Go will be introduced. TypeScript 6.0 retains the current TypeScript/JavaScript compiler but includes changes to facilitate migration. The tsgo compiler will speed up builds, reduce memory usage, and improve scalability in large projects.

The TypeScript 7.0 preview release is available via VSCode and NPM. The 6.x and 7.x branches will coexist until the new one reaches full maturity.

TypeScript extends JavaScript with static typing, classes, and library compatibility. It compiles to JS for browsers, Node.js, Bun, Deno.

New Import and Type Features

Added support for #/ prefixes to import module aliases, like in Node.js:

import utils from '#root/utils.js';

This eliminates the need for relative paths like ../../utils.js.

The --stableTypeOrdering flag enables deterministic type ordering from 7.0. It ensures consistent ordering across environments but slows compilation by 25% in 6.0. Use it for diagnostics before migration.

Built-in types for the Temporal API: date manipulations with or without time zones, conversion, formatting, arithmetic.

Added getOrInsert and getOrInsertComputed to Map and WeakMap — upsert methods that return the value or create an entry.

RegExp.escape escapes special characters for safe use in new RegExp().

Default Configuration Changes

Updated default tsconfig.json settings for performance and modernity:

• rootDir = "." (directory containing tsconfig.json).
• types = [] (explicit specification, excluding all @types; speeds up compilation by 20-50%).
• target = es2025 (es5 is outdated, minimum es6).
• strict enabled by default.
• module = esnext (ESM instead of CommonJS).

Deprecated Options for Optimization

To improve performance, the following are now deprecated:

• --baseUrl.
• module Foo { ... } (use namespace Foo { ... } instead).
• --outFile (esbuild, Rollup, Webpack recommended).
• --moduleResolution: classic (switch to nodenext or bundler).

These changes simplify the transition to tsgo and optimize builds.

Key Takeaways

• TypeScript 6.0 is the final version with the old compiler; 7.0 will switch to typescript-go for speed and scalability.
• New features: #/ imports, Temporal types, Map upsert, RegExp.escape.
• Default settings stricter: strict on, es2025 target, empty types.
• --stableTypeOrdering flag for migration testing (slows by 25%).
• Parallel support for 6.x and 7.x until the new branch matures.

This version positions the project for the future with a focus on performance in monolithic codebases.

— Editorial Team