API & OpenAPI Glossary
Clear, developer-centric definitions and practical code examples for essential web API terminology.
OpenAPI Specification (OAS)
The OpenAPI Specification (OAS) is an open-source, machine-readable standard format for defining, describing, consuming, and visualizing RESTful web services.
SWAGGERSwagger
Swagger is a popular suite of open-source and commercial developer tools built around the OpenAPI Specification, including Swagger UI, Swagger Editor, and Swagger Codegen.
API-DESIGNREST API
Representational State Transfer (REST) is an architectural style for designing networked applications using stateless communications and standard HTTP methods.
OPENAPIJSON Schema
JSON Schema is a vocabulary that allows you to annotate and validate JSON data structures.
API-DESIGNAPI Contract
An API Contract is a formal, binding specification defining the endpoints, inputs, outputs, error conditions, and SLA guarantees agreed upon between API providers and consumers.
API-DESIGNAPI Versioning
API Versioning is the practice of managing changes to an API specification across multiple released iterations without breaking existing client integrations.
API-DESIGNIdempotency
In HTTP APIs, an operation is idempotent if executing it multiple times with the same parameters produces the exact same side-effect state on the server as executing it a single time.
API-DESIGNPagination
Pagination is the technique of breaking large result sets into discrete chunks or pages returned over successive API requests.
API-SECURITYRate Limiting
Rate limiting restricts the number of API requests a client can make within a specified time window.
API-SECURITYOAuth 2.0
OAuth 2.0 is an industry-standard authorization framework enabling third-party applications to obtain limited access to user accounts without exposing user credentials.
API-SECURITYBearer Token
A Bearer Token is a security credential sent in the HTTP Authorization header (e.g. Authorization: Bearer <token>) granting access to protected API resources.
API-DESIGNHTTP Status Code
A 3-digit integer issued by a server in response to a client's HTTP request, indicating whether the request succeeded or failed.
DEVELOPER-TOOLSAPI Gateway
An API Gateway is a server component acting as a single entry point for client applications to route requests, enforce security, apply rate limits, and perform transformation tasks.
OPENAPISchema Validation
Schema Validation is the automated process of checking whether a data structure matches a target JSON Schema or OpenAPI data model.
API-DOCUMENTATIONAPI Documentation
API Documentation provides developer instructions on how to effectively integrate with and consume an API, including endpoint reference guides, tutorials, code samples, and authentication instructions.