TypeScript 7 just hit release candidate, and it's a full rewrite of the compiler from TypeScript into Go that runs around 10 times faster. We type check the real Playwright repo to watch it drop from 6 seconds to 0.87, then go through the shared memory parallelism, the new checkers and builders flags, the rewritten watch mode, and whether there are any breaking changes you need to worry about before upgrading. Same errors, same files, just a fraction of the time.

🔗 Relevant Links
https://devblogs.microsoft.com/typescript/announcing-typescript-7-0-rc/

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📌 Chapters:
0:00 - Intro
0:26 - Porting TypeScript to Go
0:57 - Playwright Benchmark
1:37 - Single Threaded Mode
1:52 - Checkers and Builders Flags
2:29 - Rewritten Watch Mode
3:00 - Breaking Changes
3:46 - Unicode Template Literals
4:18 - Release Date and Wrap Up

YouTube

TypeScript 7 release candidate is out, featuring a complete rewrite of the TypeScript compiler from TypeScript/JavaScript to Go. The rewrite delivers roughly 10x faster type checking — benchmarks on the Playwright repo show a drop from ~6 seconds to ~0.87 seconds. Key improvements include multi-core parallelism (previously single-threaded), new `--checkers` and `--builders` flags for controlling parallel workers, and a rewritten watch mode. The only language-level change is that template literal types now correctly preserve Unicode code points. Upgrading from TypeScript 6 to 7 should have no breaking changes; going from 5 to 7 requires passing through 6 first. A stable programmatic API for tooling authors is planned for 7.1, with a compatibility package to run v6 and v7 side by side.

TypeScript is not TypeScript anymore...