What is an API endpoint?

The Postman Team

June 20, 2023

An API endpoint is a URL that acts as the point of contact between an API client and an API server. API clients send requests to API endpoints in order to access the API’s functionality and data.

A typical REST API has many endpoints that correspond to its available resources. For instance, an API that powers a social media application would likely include endpoints for users, posts, and comments. Requests to API endpoints must include a method, which indicates the operation to be performed, as well as the necessary headers, parameters, authentication credentials, and body data.

Here, we’ll explore how API endpoints work, before reviewing some best practices for designing and developing them. We’ll also review the differences between a REST endpoint and a GraphQL endpoint—and discuss how the Postman API Platform can help teams produce and consume API endpoints with ease.

How do API endpoints work?

API endpoints work by connecting API clients and servers—and handling the transfer of data between them. A well-designed API should have clear and intuitive endpoints that provide a predictable way for clients to interact with the server’s resources. For example, a REST API that powers a simple blogging application might have the following endpoints, which can be accessed with the indicated HTTP methods:

• /authors – to retrieve a list of users (GET) or create a new user (POST)
• /authors/:id – to retrieve a specific user (GET), update an existing user (PUT or PATCH), or delete a specific user (DELETE)

• /articles –  to retrieve a list of articles (GET) or create a new article (POST)
• /articles/:id – to retrieve a specific article (GET), update an existing article (PUT or PATCH), or delete a specific article (DELETE)

In this example, we can see that the API exposes two sets of endpoints: one for the Author resource and one for the Article resource. Each resource can be accessed through two different endpoints, depending on the type of operation the client would like to perform. For example, if the client is interested in seeing all of the authors in the database, it would send a GET request to the /authors endpoint. In contrast, the /authors/:id endpoint enables the client to view, update, or delete a specific author’s data by including the author’s id as a request parameter.

The API client is responsible for assembling and sending the request to the API server. In addition to the endpoint and method, which are required, the request may also include parameters, HTTP headers, and a request body. Let’s explore those request components a little further:

• Parameters are variables that are passed to an API endpoint, and they provide specific instructions for the API to process. For example, the /articles endpoint of our simple blogging application might accept a category parameter, which it would use to retrieve articles of the specified category.
• Request headers are key-value pairs that provide additional information about the request. For instance, the Accept header specifies the media types that the client can accept, while the Authorization header is used to send tokens and API keys to authenticate the client.
• A request body includes the actual data that is required to create, update, or delete a resource. For instance, if an author wants to create a new article in our example blogging application, they would send a POST request to the /articles endpoint with the content of the article in the request’s body.

Once the client sends the request to the appropriate endpoint, the API server authenticates it, validates the input, retrieves or manipulates the relevant data, and returns the response to the client. The response typically includes a status code, which indicates the result of the request, as well as a body, which contains the actual data that the client requested (if the request was successfully executed).

What are some best practices for designing and developing API endpoints?

API endpoints are essential to the health and performance of any application. The following best practices can help you design, develop, and maintain endpoints that are reliable, scalable, user-friendly, and secure.

Create a predictable and intuitive API endpoint structure

It’s important to use a clear and intuitive naming convention and structure when defining your API’s endpoints. When possible, the same conventions should apply to every API in your digital portfolio. This consistency will help create a predictable user experience for your API’s consumers, making it easier for them to integrate with your API.

Implement secure authentication mechanisms

API endpoints are the doorways to an application’s data, which makes them appealing attack targets. API authentication involves verifying the identity of a client that is making an API request, and it plays a crucial role in strengthening an API’s security posture. It’s therefore important to leverage well-established authentication mechanisms—such as OAuth, OpenID Connect, or JWT—especially if your endpoints provide access to sensitive data.

Validate and sanitize input data

Input validation is the process of confirming that any data that’s sent to the API follows the expected format and constraints, while sanitization helps ensure that input data does not include harmful characters. These processes should be performed at the method level in order to prevent any malicious code from entering the workflow, where it might alter permissions or database records.

Clearly document every API endpoint

API documentation plays an important role in the overall success of an API. Private API documentation facilitates cross-team collaboration and reduces code duplication, while public API documentation helps potential consumers understand and experiment with an API. It’s therefore crucial for API producers to thoroughly document every API endpoint, including its methods, parameters, and accepted data types. They should also describe—in plain language—what each endpoint is intended to do.

Continually test and monitor your API endpoints

API testing helps ensure that an API’s endpoints work as expected—even as the API evolves. Unit tests confirm that a single endpoint returns the correct response to a given request, while end-to-end tests validate complex workflows that may involve multiple endpoints. API test automation can help teams automatically surface issues throughout the development process, while API monitoring leverages the same logic to keep tabs on an API’s endpoints once they are in production.

What is the difference between a REST endpoint and a GraphQL endpoint?

Related: GraphQL vs. REST

This article has used REST API endpoints as examples because REST is the most commonly used API architecture today. However, there are many other API architectures and protocols, including GraphQL, which is an open source query language for APIs.

There are significant differences between REST and GraphQL endpoints. REST APIs include many endpoints that return fixed data structures, which can require the client to chain multiple requests together in order to obtain the exact data it needs. For instance, a user of a blogging app might be interested in seeing all posts by an author named Jane Doe. That user might therefore send a GET request to the /authors endpoint and include “Jane Doe” as the value for a name query parameter. The response would include Jane Doe’s ID, which the user would then include in a subsequent, chained request to the /authors/:id/articles endpoint.

In contrast, GraphQL enables clients to interact with a single endpoint and specify the exact data they need—without having to chain multiple requests together. This approach reduces the number of round trips between the client and the server, which can improve reliability and performance by reducing the amount of data that is transferred.

How can Postman help you design, develop, and test your API endpoints?

The Postman API Platform includes a powerful feature set that enables teams to design, develop, and consume API endpoints. With Postman, you can:

• Explore and debug endpoints with a fully-integrated API client: The Postman API client includes support for REST, GraphQL, SOAP, WebSocket, and gRPC, which makes it easier to send requests and interpret responses from any API.
• Generate and publish API documentation: Postman enables users to automatically generate API documentation for any OpenAPI 3.0 definition, which includes information about each endpoint, operation, and data model. API producers can also publish their documentation alongside their workspaces and collections in the Postman API Network, which helps consumers explore and begin working with the available endpoints.
• Create, run, and automate an API test suite: Postman users can create tests for their endpoints with a code-snippet library—and use the Collection Runner to test requests in specific sequences. They can also automate test executions on Postman Cloud or within their CI/CD pipelines.
• Monitor endpoint performance and response times: Postman enables you to monitor your endpoints’ health and performance with collection-based monitors, which can be run manually, on a schedule, and in various regions.
• Leverage built-in support for a wide range of authentication mechanisms: Postman provides built-in support for several authentication types, including OAuth 2.0, API keys, JWT bearer tokens, and AWS signature. This feature streamlines the authentication process and makes it easier to start working with a new API.