TypeScript 6.0 Migration Guide Released Ahead of Changes

Why it matters

- Several compiler options will change their defaults to align with modern practices; for example, `strict` will be enabled by default, `target` will default to `es2025`, and `module` will default to `esnext`. The `types` compiler option will now default to an empty array, which could lead to 20-50% build time improvements by preventing the automatic inclusion of all packages in `node_modules/@types`. - This release deprecates several legacy options in preparation for their complete removal in version 7.0, including the `target: es5` option and older module systems like `amd`, `umd`, and `system`. Teams can temporarily silence deprecation warnings by setting `"ignoreDeprecations": "6.0"` in their tsconfig, but this escape hatch will not exist in 7.0. - The official timeline places the final release of TypeScript 6.0 on March 17, 2026, with version 7.0 planned to be released shortly after 6.0 stabilizes. The current JavaScript-based codebase is now in maintenance mode, receiving only critical fixes and changes that align with the future Go-native version. - New features are also included, such as built-in types for the Stage 3 Temporal API, which is a modern replacement for the `Date` object, and support for `RegExp.escape`. - The primary driver for these changes is the upcoming TypeScript 7.0, a complete rewrite of the compiler and language service in Go, codenamed "Corsa". This port to a native, multi-threaded language is projected to decrease most build times by a factor of 10 and significantly reduce memory usage. - The decision to use Go over a language like Rust was a pragmatic one; Go's garbage collector and structural similarity to the existing TypeScript codebase are expected to make the port more manageable while still providing significant performance gains. - From a platform leadership perspective, this migration represents a "controlled demolition" of technical debt. It forces the adoption of modern standards (like ES Modules and stricter type-checking) before the major architectural shift in 7.0, making it a critical exercise in organizational readiness. - For teams integrating AI into their platforms, the performance enhancements in 7.0 could dramatically speed up developer feedback loops, especially in large monorepos where language server performance is a bottleneck. Faster type-checking in CI/CD pipelines will accelerate the validation and deployment of AI-assisted code generation.

Key numbers

• A migration guide for the upcoming transition from TypeScript 5.x to 6.0 has been published.
• The new version will introduce new defaults and deprecations, laying the groundwork for a future Go-native version 7.0, and platform teams are advised to begin proactive migration planning.
• - Several compiler options will change their defaults to align with modern practices; for example, strict will be enabled by default, target will default to es2025, and module will default to esnext.
• The types compiler option will now default to an empty array, which could lead to 20-50% build time improvements by preventing the automatic inclusion of all packages in node_modules/@types.

What happens next

• Several compiler options will change their defaults to align with modern practices; for example, strict will be enabled by default, target will default to es2025, and module will default to esnext.
• The types compiler option will now default to an empty array, which could lead to 20-50% build time improvements by preventing the automatic inclusion of all packages in node_modules/@types.
• This release deprecates several legacy options in preparation for their complete removal in version 7.0, including the target: es5 option and older module systems like amd, umd, and system.

Sources

• has been published
• Several compiler options
• The types compiler
• This release deprecates
• The official timeline
• This port to a native
• The decision to use
• From a platform leadership
• For teams integrating

Quick answers