using-runtime-checks

Runtime validation uses schema libraries like Zod to check external data against defined structures at execution time. Define a schema, call safeParse or parse on incoming data, and receive either typed results or detailed validation errors for safe downstream handling.

TypeScript's types exist only at compile time and vanish after build. Runtime validation bridges this gap by checking actual data from APIs, user input, and third-party sources, preventing type-mismatch errors that compile-time checks cannot catch.

Yes. Schema libraries like Zod generate TypeScript types directly from your schema definitions, eliminating manual type duplication and ensuring your runtime validation and compile-time types stay synchronized.

Use safeParse to return a result object containing either validated data or detailed error information without throwing exceptions. Inspect the result's success flag and access typed errors or data accordingly for graceful error propagation.

Yes. Runtime validation applies to any untrusted external data: API responses, form submissions, webhook payloads, and third-party service outputs. Define schemas for each data source and validate before using data in your application.

Centralize schema definitions alongside their corresponding TypeScript types, typically in dedicated validation or schema modules. This keeps validation logic colocated with type definitions and makes schemas reusable across route handlers, services, and middleware.