But how is the below possible - doesn't it need to include most of the TypeScript compiler? Does it compile the type definitions to some kind of validation structure (like how a compiled regex works) and then use just that?
- Zero external dependencies
- Works in Node.js and all modern browsers
- Tiny: 2kb core bundle (gzipped)
The TypeScript compiler is only needed during development, the compiled JavaScript code contains no TypeScript-specific logic. Zod’s validation is entirely JavaScript-based, relying on simple checks (e.g., typeof, regexes, comparisons).
Also, the 2kb bundle just for the zod/v4-mini package, the full zod/v4 package is quite large.
I think Zod uses JIT compilation via `new Function`, rather than including the entire TypeScript compiler. This method allows for concise validation logic, executing only what’s necessary at runtime.
