What is a REST API?
A REST API is an interface that is based on the principles of the REST architecture (Representational State Transfer) and enables communication between distributed systems via HTTP. It defines how clients interact with servers by identifying resources and retrieving or modifying them using standardized HTTP methods.
Basic principles of a REST API
A REST-compliant API follows certain architectural principles:
- Stateless: Each request must contain all required information, as the server does not store any session data.
- Client-server architecture: The separation of client and server improves scalability and flexibility.
- Uniform interface: Standardized endpoints and data formats such as JSON or XML ensure consistent use.
- Cacheability: Responses can be cached to improve performance.
- Layered architecture: The API can be implemented across several layers without the client knowing the details of the underlying layers.
- HATEOAS (optional): Hypermedia as part of the API response enables dynamic navigation through resources.
HTTP methods in REST APIs
REST APIs use standardized HTTP methods to manipulate resources:
- GET: Retrieves a resource (e.g.
GET /users/{id}provides user data). - POST: Creates a new resource (e.g.
POST /userscreates a new user). - PUT: Updates an existing resource completely (e.g.
PUT /users/{id}). - PATCH: Partially updates a resource (e.g.
PATCH /users/{id}). - DELETE: Deletes a resource (e.g.
DELETE /users/{id}).
Data formats and API responses
REST APIs usually use JSON as the standard format for requests and responses. Typical HTTP status codes provide information about the success or error of a request:
- 200 OK: Successful request.
- 201 Created: Resource successfully created.
- 400 Bad Request: Invalid request.
- 401 Unauthorized: Missing authentication.
- 403 Forbidden: No authorization for the resource.
- 404 Not Found: Resource not found.
- 500 Internal Server Error: Server-side error.
URI design for REST APIs
RESTful APIs follow a clear and intuitive URI structure:
- Resources are represented by nouns (
/users,/orders). - Hierarchies are separated with
/(/users/{id}/orders). - Filters and queries use query parameters (
/users?status=active). - No verbs in URIs (instead of
/getUsers, correct would be/users).
Security and authentication
REST APIs require security mechanisms for access control:
- OAuth 2.0: Standard protocol for authorization.
- JWT (JSON Web Token): Token-based authentication.
- API keys: Static keys for API access.
- HTTPS: Encryption for secure data transmission.
- Rate limiting: Protection against API misuse.
REST and IT standards: standardized interfaces for maximum interoperability
REST is not an independent standard, but an architectural style that is based on the principles of the web. Nevertheless, there are numerous IT standards that structure, secure and optimize REST APIs. These standards ensure interoperability, security and efficient integration into modern software architectures.
HTTP – The foundation of REST
REST is based entirely on HTTP (Hypertext Transfer Protocol), the most important protocol for communication on the web.
The standard methods are:
- GET – retrieve data
- POST – send data
- PUT – update resources
- DELETE – delete resources
- PATCH – partly update a resource
Since HTTP is used worldwide, REST APIs are natively compatible with any platform or programming language that supports HTTP.
OpenAPI / Swagger – Standardized API description
Since REST APIs can be designed differently, OpenAPI (formerly Swagger) helps to define a standardized specification for endpoints, parameters and responses.
OpenAPI enables:
✅ Automatic API documentation
✅ Interactive API tests (Swagger UI, Postman)
✅ Code generation for client and server implementations
OAuth 2.0 & JWT – Standardized API authentication
As REST APIs are often publicly accessible, they require secure authentication methods:
- OAuth 2.0 allows third-party applications to authenticate securely (e.g. login with Google/Facebook).
- JSON Web Tokens (JWT) enable token-based authentication that is stateless and scales well with REST.
API governance & versioning
To ensure compatibility over time, REST APIs use proven governance practices:
- API versioning (v1, v2, …) to control changes
- Rate limiting & throttling to avoid overloading
- CORS (Cross-Origin Resource Sharing) to control API accesses
REST vs. alternative API-Standards (GraphQL, gRPC, SOAP)
While REST is widely used, alternative standards exist for special use cases:
- GraphQL (queries exactly as required, no overfetching problems)
- gRPC (binary protocol for fast microservice communication, HTTP/2-based)
- SOAP (older XML-based API protocol with strict standards, often used in enterprise systems)
REST as a flexible standard with broad support
REST APIs benefit from established web and security standards, which ensures their interoperability, scalability and security. Thanks to HTTP, OpenAPI, OAuth 2.0 and API governance, REST APIs are flexible, widely used and future-proof – and therefore remain a key technology in modern software development. 🚀
Areas of application for REST APIs
REST APIs are widely used due to their flexibility:
- Web and mobile applications: Communication between frontend and backend.
- Microservices: Integration of distributed systems.
- Cloud services: Connection of external APIs such as AWS, Google Cloud.
- IoT (Internet of Things): Control of networked devices.
- Data integration: Exchange between systems in companies.
REST API: The strengths and weaknesses at a glance
REST APIs are the de facto standard for communication between distributed systems and form the backbone of modern web applications, microservices and mobile apps. However, like every technology, REST also has its strengths and weaknesses, which must be taken into account when making architectural decisions.
REST APIs are without question the most widely used interface technology – but are they really the best choice for every use case?
While their simplicity and standardization offer clear advantages, there are also challenges that come into play with complex architectures and modern requirements.
Here you will find the most important advantages and disadvantages at a glance:
Advantages of REST APIs
✅ Simple and widespread.
✅ Uses standardized HTTP methods.
✅ Platform- and language-independent.
✅ Scalable thanks to stateless principle.
✅ Well suited for public and internal APIs.
Platform independence & broad support
REST is based on the open standards of the Internet (HTTP, JSON, XML), which means that almost any technology can consume RESTful APIs – from web and mobile applications to IoT devices and microservices.
Scalability thanks to the stateless principle
Because each REST request does not store state, servers can scale more efficiently by processing requests independently. This is ideal for distributed systems that have to cope with high loads.
Simple implementation & maintenance
REST APIs can be developed and extended quickly using common frameworks. The standardized use of HTTP methods and status codes makes integration intuitive and easy to understand for developers.
Caching for performance optimization
REST supports client and server caching, which reduces repeated requests and improves performance. This is particularly beneficial for APIs that provide frequently read data.
Flexibility through JSON & XML
REST APIs can provide data in different formats, most commonly in JSON (lightweight structure) or XML (structured and extensible). This enables adaptation to different system requirements.
High interoperability & integration
REST APIs are particularly well suited for integration between different applications. This makes them the preferred choice for external interfaces, Open APIs and public data services (e.g. OpenWeatherMap, GitHub API).
Disadvantages of REST APIs
❌ Overfetching & underfetching: clients receive too much or too little data.
❌ No real-time communication (in contrast to WebSockets).
❌ Missing schema definition (compared to GraphQL).
Overhead due to repeated requests
As REST requests do not save any status, each request must transmit all the necessary information (e.g. authentication, session data) again. This can lead to a high overhead for complex applications.
Inefficiency with complex data structures
REST APIs often deliver more data than is actually required (overfetching) or too little (underfetching), so that multiple requests are necessary. GraphQL solves this problem better by allowing well-defined queries.
Lack of real-time functionality
REST is a request-response-based model that does not support bidirectional communication. WebSockets or gRPC are better suited for real-time applications (e.g. chats, streaming).
Lack of standardization for API designs
Although REST is an established concept, there is no fixed specification as to exactly how an API must be structured. This often leads to different design approaches, which makes the consistency and reusability of APIs more difficult.
Security requires additional effort
REST APIs require additional security measures as they are often publicly accessible. OAuth, JWT, API rate limiting and CORS are necessary to prevent misuse and unauthorized access.
Scaling can be costly
While REST scales well, efficient load balancing often requires additional components such as API gateways, load balancers and reverse proxies. This increases the complexity of the infrastructure.
REST APIs are an essential component of modern software development. They enable efficient and scalable communication between systems and are used in web and cloud applications, microservices and IoT environments. Despite some disadvantages, they remain the preferred choice for many API architectures due to their simplicity and broad support.
Conclusion: When is REST the right choice?
REST APIs are simple, flexible and proven, but not ideal for all scenarios. They are the right choice for:
✅ Web and mobile applications that require a simple and scalable API
✅ Microservices that communicate with each other via standardized interfaces
✅ Public APIs that enable standardized use by third-party providers
✅ Data access that does not require real-time communication
However, if real-time interactions, highly structured data queries or low latency are required, GraphQL, gRPC or WebSockets may be more suitable.
REST is a strong foundation, but depending on the use case, it is worth taking a look at modern alternatives. 🚀
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