Compatibility

tsz is not a drop-in replacement yet. Even though TypeScript's own compiler tests pass, some benchmark projects still do not compile cleanly with tsz. There is still a lot of compatibility work to do before it can replace tsc on real projects.

Currently tracking TypeScript 6.0.3.

Type Checking

The conformance suite compares tsz diagnostics with tsc on TypeScript's own compiler tests. This is the main signal for whether tsz agrees with tsc about types and errors.

Type checking

99.9%

12,578 of 12,585 compiler tests match tsc.

Emit

Emit compatibility means the generated output matches what TypeScript users expect from tsc. JavaScript emit and declaration emit are tracked separately because they fail for different reasons and matter to different users.

JavaScript emit

99.2%

Declaration emit

97.1%

JavaScript emit is at 99.2% (1 skipped). Declaration emit is at 97.1% (11,862 skipped).

Language Service

The language-service suite checks editor-facing behavior: completions, hover, go-to-definition, diagnostics, and related workflows that developers feel in an IDE.

Editor behavior

99.9%

6,558 of 6,562 editor tests match the TypeScript suite.