validating-external-data

Runtime validation ensures external data matches expected types before your application uses it. Use schema validation libraries like Zod to parse and validate API responses, JSON payloads, and user input against defined schemas, catching type mismatches at boundaries rather than causing runtime errors later.

External data from APIs and JSON sources is untrusted and may not match your expected schema. Runtime validation prevents type errors, security vulnerabilities, and unexpected application behavior by enforcing strict type checking at data entry points before processing.

Schema validation libraries provide structured error details when data fails validation. Capture these errors at boundaries, log them for debugging, and return clear error responses to clients so invalid data is rejected before reaching your application logic.

Yes. Schema-based validation libraries like Zod automatically infer strongly typed interfaces from your schema definitions, eliminating manual type declarations and keeping runtime validation and static types synchronized.

Validate all untrusted external data: API responses, JSON payloads, user input, environment variables, files, and message queues. Apply validation at every runtime boundary where external data enters your application.