Fastify JSON Schema Validation: Decision Guide and Implementation
Learn when to use Fastify's built‑in JSON Schema for request validation and response serialization, see trade‑offs, and view a shared‑schema example.
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Learn when to use Fastify's built‑in JSON Schema for request validation and response serialization, see trade‑offs, and view a shared‑schema example.
Stop relying on implicit API contracts. Learn how to use JSON Schema to enforce data integrity, handle polymorphism, and prevent breaking changes in distributed systems.
Learn how to use OpenAPI 3.0 component schemas to eliminate redundancy, prevent schema drift, and maintain strict data boundaries between request and response models.
Schema mismatch in version migration Migrating an API definition from OpenAPI Specification (OAS) 3.0 to 3.1 introduces a fundamental shift in how schemas are handled, specifically the alignment of OAS 3.1 with JSON Schema Draft 2020-12. This change alters the structural requirements for data validation and property definitions. When updating the openapi ver
Stop chasing 'undefined' errors in your API. Learn how to use JSON Schema to enforce structural integrity, type safety, and polymorphic data validation before requests hit your logic.
Learn when to use Fastify's built-in JSON Schema validation versus custom preHandler logic to optimize API performance and maintain data integrity.
Stop writing repetitive validation logic. Learn how Fastify uses JSON Schema and fast-json-stringify to automate input validation and prevent accidental data leaks in your API responses.
Fastify handles incoming JSON payloads and query strings by passing date-formatted strings directly to the application logic. When using JSON Schema validation with format: 'date-time' , the framework ensures the string conforms to ISO 8601, but the actual conversion to a JavaScript Date object typically occurs within the handler or via a custom coercion lay
Compatibility boundary between nullable: true and JSON Schema type arrays I maintain an OpenAPI document that describes a REST API consumed by several downstream teams, each running their own validation and code-generation pipelines. The spec currently declares openapi: 3.0.3 and uses nullable: true on a number of schema properties. I want to adopt 3.1.0, wh