An API (Application Programming Interface) allows different software systems to communicate with each other by calling features and accessing data. APIs make it possible for applications to integrate and share information seamlessly. The core components that make up an API include:

API Endpoints

The endpoints represent each URL that is available in an API. API Endpoints refer to the different requests that can be made, and each endpoint has its own specific function.

For example, an API may have endpoints like:

/users - Retrieve a list of users
/users/123 - Get details of user with ID 123
/posts - Create a new blog post

The endpoints define the structure of an API and the operations that are possible. Well-designed APIs will provide sensible naming and structure for endpoints that group related functionality.

HTTP Request Methods

APIs use HTTP request methods to indicate the desired action to perform for an endpoint. The main HTTP methods include:

GET - Retrieve a resource
POST - Create a new resource
PUT - Update an existing resource
DELETE - Delete a resource

By specifying the HTTP method, the API call indicates whether it is fetching data, modifying data, or performing another action. This guides both the API server and client on the intent of the request.

Request Parameters

Parameters provide a way to filter API requests by sending additional data. They allow the API calls to be more flexible and dynamic.

Common types of parameters include:

Query string - Appended to the endpoint URL like /users?status=active
Path - Inserted into the endpoint path like /users/{id}
Header - Sent as custom headers like Authorization
Body - Sent in the request body, often for POST/PUT requests

Parameters enable things like pagination, sorting, filtering, and more.

Request Headers

In addition to standard headers like Content-Type, APIs can accept custom headers that provide additional context and functionality. Headers may be used for things like:

Authentication - Sending tokens or credentials
Providing API version information
Indicating the response format needed
Adding rate-limiting context like tokens

Headers make it easy to pass metadata for an API request without having to put it in the URL or body.

Request Body

For POST and PUT requests that create/update resources, the body contains the data itself. The body can be formatted in JSON, XML, or other formats.

The body allows complete resources or datasets to be sent, rather than just individual parameters. For example, sending all details of a new blog post in the body.

API Client

The API client refers to any application or system calling the API. This may be a mobile app, web app, IoT device, or other consumer of the API. The client initiates requests to the API.

API Response

The response provides the requested data or confirmation of the result. It will contain status codes, response headers, and usually response data.

Common response codes like 200 OK, 404 Not Found, and 500 Server Error indicate the outcome. The headers provide metadata like pagination. The body contains the returned information in JSON, XML, HTML, or other formats.

Well-designed responses make it easy for API consumers to check the result and retrieve the response data.

Status Codes

Status codes are a core part of API responses. They indicate whether the request succeeded (2xx), failed due to client-side issues like 404 (4xx), or failed due to server-side problems like 500.

Common codes include:

200 OK - Request succeeded
201 Created - Resource was successfully created
400 Bad Request - Malformed request
404 Not Found - Requested resource doesn't exist
500 Server Error - Internal server error

These standardized codes make it easy for developers to programmatically check for issues.

Authentication

Public APIs require authentication to identify application developers and restrict access. Common methods include:

API Keys - Unique tokens assigned to each developer
OAuth - Token-based authentication where apps get limited access
Basic Auth - Sending username/password with the request

Authentication ensures the API is only used by approved developers.

Documentation

Complete API documentation is crucial for developers to understand how to use it. Documentation should provide:

Overview of API capabilities
Details on authentication methods
Information on endpoints, parameters, headers, body
Example requests and responses
Guidance on error handling
Changelog of API additions and updates

Thorough documentation enables developers to quickly learn how to use the API correctly.

This covers the main components that make up a typical API structure. Well-designed APIs will incorporate these elements in a standardised way that makes the API easy to use and integrate with.

Apidog: Your Ultimate API Documentation Tool

Apidog is your go-to solution for comprehensive API documentation. With user-friendly features like real-time updates, data schema capabilities, and online debugging, it simplifies the creation, management, and sharing of API documentation, making it an essential companion for developers, teams, and organizations involved in API development.

Highlight of Apidog:

Real-Time Updates: The Change History feature tracks and manages modifications made to your API documentation over time. It provides version comparison and rollback options, facilitating collaboration among team members. Any changes made to the API documentation are promptly reflected in the shared online version, ensuring that everyone has access to the latest information.
Share Online: You can publish and share your API documentation online with specific team members or stakeholders. Apidog allows for customization of access, language, sharing scope, and online debugging, making it a breeze to collaborate and communicate effectively.
Batch API Management: For projects dealing with multiple APIs, Apidog simplifies tasks like bulk deletion, status modification, and tag management. This feature enhances API management efficiency and organization within your project.
Online Debugging: Apidog's online documentation includes a built-in debugging environment, allowing team members to test and validate APIs directly within the documentation. This feature streamlines the development and troubleshooting process.

What are the 4 Major Types of API?

APIs can be categorized into different types based on who is intended to consume them:

Public APIs

Open APIs, also known as public APIs, are accessible to external developers and are intended for wider public use. They are typically well-documented and openly available for integration. Companies often use open APIs to expand their product or service's reach and functionality, allowing third-party developers to build applications or services that interact with their platforms.

Examples of public APIs include:

Twitter API - Access tweets and users data
Stripe API - Integrate payments processing

Partner APIs

Partner APIs are shared with specific business partners and collaborators. These APIs are often used to establish connections and facilitate data sharing between organizations. Partner APIs require an agreement or contract to access, and they provide a more controlled and secure way to exchange information.

Examples include:

PayPal APIs for platform partners
Amazon Marketplace APIs for sellers

Internal APIs (Private APIs)

Internal APIs, or private APIs, are designed for internal use within a company or organization. These APIs enable different teams or departments to communicate and share data between their systems. Internal APIs aim to improve workflow and connectivity for employees.

Examples are:

HR system APIs for use by payroll systems
Inventory APIs for internal warehouse apps
Data analytics APIs for internal reporting dashboards

Composite APIs

Composite APIs, also known as custom APIs, are created by combining various other APIs. They serve as a wrapper around multiple APIs to provide a single, unified interface. Composite APIs are useful when a specific function requires data from multiple sources or when you need to simplify complex interactions.

This categorization covers the major API types based on the intended consumer audience. It provides a model for controlling access and customizing support accordingly.

How do APIs work?

APIs provide a structured way for different software applications to communicate and share data. We sincerely recommend test your API with Apidog.

The interaction typically functions as follows:

Example: Weather API

Suppose you're building a weather application, and you want to include a feature that provides the current weather for a specific location. To do this, you can use a weather API.

1.Request:Your application sends an HTTP request to the weather API server, including the location for which you want weather information. For example, you might send a request like this:

GET https://api.weather.com/current?location=NewYork

2.Processing:The weather API server receives the request, extracts the "NewYork" location parameter, and looks up the current weather information for New York in its database.

3.Response:The server then formats the weather data into a JSON response, like this:

{
  "location": "New York",
  "temperature": 72°F,
  "conditions": "Partly Cloudy"
}

4.Transmission:It sends this JSON response back to your application.

5.Client-Side Processing:Your weather application receives the JSON response, extracts the weather data, and displays it to the user. For example, it might show "New York: 72°F, Partly Cloudy" on the screen.