4 Different Types of APIs and When to Use Each


4 Different Types of APIs and When to Use Each

In this day and age, it’s very safe to say you interact with different APIs on a daily basis, even if you don’t realize it. From your favorite social media app to checking the weather, APIs are the driving force behind making these services accessible to you. Application programming interfaces, act as intermediaries that facilitate communication between different software systems.  APIs define the types of requests possible within a system, how to make them, and what data to expect in response. 

APIs are essential in modern software development, enabling developers to integrate different applications, services, and data sources quickly and easily.  If you’re in the least tech-savvy, you’re probably familiar with them and how they facilitate smooth communication between different software systems, and perhaps how they’re implemented.

There are multiple ways of grouping APIs and in today’s post, we’ll be looking at the two main ways: accessibility and architecture. The latter is mostly in the context of web APIs, which are the most common type of APIs in modern software development. 

Based on accessibility, we, have four major types of APIs:

  1. Open/Public APIs
  2. Internal/Private
  3. Partner/External
  4. Composite APIs

By architecture, there are five main types:

  1. REST
  2. SOAP
  3. GraphQL
  4. RPC
  5. Webhooks

We’ll explore each of these types of APIs in detail, explaining their applications, pros, and cons. By the end of this read, you’ll have a clear understanding of the different types of APIs and when to use each in your projects.

Open APIs

Open APIs, or public APIs, are publicly available and can be accessed by any developer. Public APIs’ design allows easy consumption and integration with other software applications, making them ideal for public-facing applications.

Developers use public APIs in a variety of applications, such as social media platforms, weather applications, and payment gateways. For example, the OpenWeatherMap API provides developers with access to real-time weather information, making it easy for developers to integrate weather information into their applications. Developers can use the Google Maps API to add location data to their apps. The Twitter API on the other hand helps access Twitter feeds and display them in their apps.

Open APIs are pretty often a piece of cake to use and integrate with other systems. They also foster collaboration and innovation by giving developers from different backgrounds the ability to build on top of existing apps. By hooking onto public APIs, you can avoid reinventing the wheel and hit the ground running.

However, if you don’t properly secure your public APIs, you could potentially open up a can of worms. Open APIs can be vulnerable to security threats, which can expose your data to malicious actors. In July last year, attackers hacked Twitter’s API and accessed 5.4 million user account details. This highlights the need for proper security measures when working with public APIs.

These types of APIs can be subject to high traffic volumes, which can lead to performance issues. Case in point, in 2020, the Slack API experienced a major outage, orchestrated by a surge in usage following the COVID-19 pandemic.

Google Maps app icon on Apple iPhone screen
Developers can use open APIs like the Google Maps API to add location data to their apps.


Internal APIs

Internal APIs, also known as private APIs, are used by companies to expose their internal systems to other teams within the same organization. They help build internal applications not meant for public use.

Companies use private APIs in a variety of applications, such as project management systems, employee directories, and inventory management systems. For example, Amazon massively uses internal APIs to allow their different departments to communicate with each other. In fact, most FAANG/MAANG companies rely heavily on internal APIs to facilitate communication between different teams and systems within the company.

Internal APIs are often more secure than open APIs since they are only accessible within an organization. They can help you promote collaboration within your organization, which can help different teams work together seamlessly. They allow you to reuse existing systems and reduce development costs, which can help you save a pretty penny.

Partner APIs

Partner/external APIs help with sharing data and services with trusted partners. They typically integrate third-party services with existing software systems, making them ideal for e-commerce applications, social media platforms, and financial services.

External APIs are used in a variety of applications, such as Amazon’s Seller API, which allows sellers to integrate their Amazon seller account with third-party software systems. By hooking onto an external third-party API, you can expand your reach and offer new services to your customers. 

You will of course want to make sure that the partner APIs you integrate with are secure as you could be putting your application and data at risk with an insecure one.

Composite APIs

Composite APIs combine multiple APIs into a single API, making it easier to access multiple services through a single endpoint. They provide a more comprehensive service to end-users, making them ideal for usage in places like e-commerce applications which need to interact with multiple APIs at the same time.

Developers often create composite APIs by combining the functionality of APIs, such as payment processing, shipping, and order tracking. This streamlines the process of accessing multiple services and data sources on an e-commerce site like eBay.

Another great example of a composite API is the Google Maps API, which combines various mapping services, such as location search, directions, and real-time traffic updates, into a single API. Developers can thus create custom applications that incorporate various mapping functionalities.

The integration of different types of APIs o course introduces a degree of complexity meaning such APIs need careful design to ensure reliability and efficiency.

Types of APIs By Architecture

APIs can be implemented in various ways based on the underlying technology and architecture used. Let’s look at the main types of APIs on this basis.


Representational State Transfer (REST), is a widely adopted architectural style for building APIs. REST APIs use HTTP methods to retrieve or modify resources and represent those resources in a format such as JSON or XML. REST APIs are stateless, meaning that each request contains all the information needed to complete that request, and the server does not keep any state between requests.

One of the significant advantages of REST APIs is their scalability. REST APIs use standard HTTP methods, making them easily cached, which reduces server load and improves performance. As well, REST APIs are highly flexible and applicable in various contexts, including web, mobile, and IoT applications.

Since there is no standard for representing or structuring resources, each API can have its own unique implementation. This could lead to inconsistencies that can make it harder for anyone new to the system to wrap around.

A popular example of a REST API is the Twitter API, which allows developers to access Twitter’s data and functionality, such as searching for tweets or posting tweets on behalf of a user.


SOAP, or Simple Object Access Protocol, is another widely used protocol for building APIs. Unlike REST APIs, which use HTTP, SOAP APIs use XML as their message format and can use various transport protocols, such as HTTP, SMTP, or FTP.

Their support for a wide range of data formats and transport protocols makes them highly versatile. SOAP APIs also provide advanced features such as built-in error handling and security mechanisms, making them suitable for enterprise-level applications.

However, SOAP APIs can also be complex to implement and consume. Because they use XML, which is more verbose than JSON, SOAP APIs tend to be slower and more challenging to work with in some contexts.

A popular example of a SOAP API is the Google AdWords API, which allows developers to manage Google AdWords campaigns programmatically.

Simple Mail Transfer Protocol. Smtp server mail transfer protocol. TCP IP protocol sending and receiving e-mail
SOAP APIs use XML as their message format, so they can use HTTP, SMTP, or FTP protocols.


GraphQL APIs

GraphQL is a query language for APIs developed by Facebook. It allows clients to specify exactly what data they need and receive only that data in response. GraphQL API types are highly efficient because they eliminate overfetching and underfetching, which are common problems with REST APIs.

GraphQL APIs offer excellent flexibility. Because clients can specify precisely what data they need, APIs can be optimized for specific use cases and contexts, such as mobile applications or IoT devices. GraphQL APIs are also highly introspectable. This means clients can query the API itself to discover available resources and data structures.

That said, GraphQL APIs presently require specialized tools and frameworks. And because they allow clients to specify their queries, there’s the additional need to validate those queries and protect against malicious or inefficient queries.

A popular example of a GraphQL API is the GitHub API, which allows developers to access GitHub’s data and functionality, such as retrieving repositories or creating issues.


RPC, or Remote Procedure Call, is a protocol for building APIs that allows clients to call methods on a remote server and receive the results of those methods. These APIs typically use a binary protocol such as Protocol Buffers to transmit data efficiently between client and server.

RPC APIs are highly performant. Because they use a binary protocol, RPC APIs they tend to be faster and more efficient than APIs that use text-based formats such as JSON or XML. RPC APIs are also highly scalable and can handle large amounts of traffic without sacrificing performance.

Nevertheless, RPC APIs can be more challenging to implement and consume than other API types. They require specialized libraries and tools to generate client and server code. They may also be less interoperable with other systems than APIs that use standard protocols such as HTTP.

A popular example of an RPC API is the gRPC API, which is a high-performance, open-source framework developed by Google. It uses Protocol Buffers as its message format and supports a variety of programming languages. WordPress XML-RPC API, which allows remote access to WordPress sites, is another example of an RPC API. It enables users to perform various tasks such as publishing posts and managing comments. However, it’s currently being deprecated in favor of the REST API.


Webhooks are a different type of API implementation that allows applications to receive notifications when specific events occur. Instead of the client making requests to the server, the server sends requests to a URL specified by the client. Real-time applications, such as chat applications typically use webhooks for notifications and alerts.

Because the server sends requests to the client, there is no need for the client to constantly poll the server for updates, which can save bandwidth and improve performance. Webhooks are also highly flexible and can be used in various contexts, including web, mobile, and desktop applications.

However, webhooks can be more challenging to implement than other API types. They require the client to provide a public URL for the server to send requests to, which can introduce security risks. Webhooks also require the client to handle and process incoming requests, which can be time-consuming and complex.

Popular examples of APIs webhooks are WhatsApp and Stripe APIs, which allow developers to handle real-time notifications of events.

Wrapping Up

APIs are a vital component in modern software development, providing developers with a way to integrate different applications and services to build innovative and powerful solutions. Whether using open APIs to quickly build new apps or creating custom internal APIs for business needs, an API will eliminate lots of legwork, allowing faster delivery. By understanding the different types of APIs and their applications, you can make informed decisions and build better, more robust applications.

4 Different Types of APIs and When to Use Each FAQs (Frequently Asked Questions) 

How do REST and SOAP APIs differ?

REST APIs are designed to be lightweight and rely on HTTP methods to manage data transmission, whereas SOAP APIs are based on XML and use more complex protocols for data exchange.

What are the key features of GraphQL APIs?

The key features of GraphQL APIs include their ability to allow clients to request exactly what data they need and in real-time. They also allow for introspection, meaning that clients can query the schema of the API and discover its capabilities. 

What are some examples of free open APIs?

There are many examples of free open APIs available for use, including the OpenWeatherMap API for weather data, the Yelp Fusion API for business reviews, the Twitter API for social media stats, and the Google Maps API for mapping data.

How do RPC APIs differ from REST APIs?

RPC APIs rely on a specific protocol, while REST APIs are protocol-agnostic. RPC APIs also use remote procedure calls to transmit data, whereas REST APIs use HTTP methods like GET and POST to send and receive data.

What’s the difference between Webhooks and WebSockets?

Webhooks are HTTP callbacks, meaning that they send data when a specific event occurs. WebSockets, on the other hand, are a bidirectional communication protocol, allowing for real-time data exchange between client and server. WebSockets are ideal for applications that require constant data updates, while Webhooks are useful for triggering specific actions based on specific events.

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