# APIs vs. SDKs: Understanding the Differences and Practical Applications
Source: https://speakeasy.com/blog/apis-vs-sdks-difference

In the interconnected world of modern software, APIs (Application Programming Interfaces) and SDKs (Software Development Kits) are indispensable tools. APIs act as the bridges that allow different applications to communicate and share data, while SDKs provide developers with the toolkits they need to build upon these APIs efficiently. Choosing whether to use an API directly or leverage an SDK is a crucial decision that can significantly impact a project's timeline and overall success. This guide will clarify the distinctions between APIs and SDKs, explore their common use cases, and outline best practices for both.

---

## Quick-Reference Summary

Here's a brief table that highlights the fundamental differences between APIs and SDKs at a glance:

| **Aspect**               | **API (Application Programming Interface)**                                       | **SDK (Software Development Kit)**                                         |
|--------------------------|-----------------------------------------------------------------------------------|----------------------------------------------------------------------------|
| **Definition**           | A set of rules and protocols for communication between software components        | A bundle of tools, libraries, and documentation to accelerate development  |
| **Scope**                | Focuses on how to send and receive data (often via HTTP/HTTPS)                    | Provides prebuilt code, testing frameworks, and platform-specific support  |
| **Implementation Detail**| Requires developers to handle requests, responses, and error handling manually    | Abstracts complexities with prewritten methods and classes                 |
| **Platform Dependency**  | Typically platform- and language-agnostic (REST, GraphQL, gRPC, etc.)             | Often tied to a specific language or ecosystem (Android SDK, iOS SDK, etc.)|
| **Use Case**             | Ideal for lightweight integration, direct control, or cross-platform scenarios    | Best for rapid development, built-in best practices, and platform-specific features |

---

## What Are APIs?

An **Application Programming Interface (API)** is a set of rules, protocols, and definitions that enable different software components to communicate. It acts as a “contract,” specifying how requests and data exchanges occur between systems, such as a client application and a remote server.

APIs serve as fundamental building blocks in modern software. They allow developers to leverage sophisticated services (e.g., payment gateways, location services) without building them from scratch. Internally, APIs make it easier for teams to create modular, scalable applications by standardizing communication between different components and services.

### Popular API Approaches

- **REST (Representational State Transfer):** REST is the most widely used approach for creating APIs, primarily due to its simplicity and compatibility with HTTP. It dictates structured access to resources via well-known CRUD (Create/Read/Update/Delete) patterns. A common pattern in modern web development is to create a front-end written in React or a similar framework, which fetches data from and communicates with a back-end server via a REST API.
- **GraphQL:** GraphQL is a newer API technology that enables API consumers to request only the data they need. This reduces bandwidth required and improves performance, and is particularly suitable in situations where a REST API returns large amounts of unnecessary data. However, GraphQL is more complex to implement and maintain, and users need to have a deeper understanding of the underlying data models and relationships in order to construct the right queries.
- **gRPC (Google Remote Procedure Call):** gRPC is a high-performance, open-source framework designed for low-latency and highly-scalable communication between microservices. gRPC is strongly-typed, which helps catch errors earlier in the development process and improves reliability. However, gRPC ideally requires support for HTTP/2 and protocol buffers, which many web and mobile clients may not support natively. Also note that far fewer developers are familiar with gRPC than REST, which can limit adoption. For these reasons, gRPC is mainly used for internal microservice communications.

In summary, REST remains the most popular API technology due to its simplicity and widespread adoption. GraphQL and gRPC are popular for specific use cases.

---

## What Are SDKs?

A **Software Development Kit (SDK)** is a comprehensive collection of tools, libraries, documentation, and code samples that streamline application development on a specific platform or for a specific service. While an API defines how to interact with a service, an SDK provides ready-made resources to speed up that interaction.

Key components of SDKs include:
- **Pre-Written Libraries**: Reduce boilerplate by offering out-of-the-box methods and classes  
- **Development Utilities**: Provide testing frameworks and debugging tools  
- **Platform-Specific Resources**: Include documentation, guides, and environment setup instructions

For example, the **Android SDK** includes compilers, emulators, libraries, and tutorials, allowing developers to build Android apps with minimal friction.

---

### Why Do SDKs Add Value to API Integrations?

Without an SDK, you must manually handle HTTP requests, parse responses, implement error handling, manage authentication, and maintain the correct sequence of API calls. SDKs solve many of these pain points by:

- **Development Efficiency**: Simplify method calls (e.g., `client.placeOrder(...)` instead of manually constructing endpoints and payloads).  
- **Type Safety & Consistency**: Strongly-typed interfaces reduce integration errors.  
- **Maintenance Benefits**: Common patterns and best practices are baked into the libraries.  
- **Change Management**: Many SDKs transparently handle minor API updates under the hood.

---

## How Do APIs Compare With SDKs in Practice?

### Example: Direct API Integration

To highlight these differences, let's look at an example of what integrating with an e-commerce API might look like, first without an SDK and then with one. The use case will be enabling a new customer to place an order. This requires fetching information about the product being ordered, creating a new customer, and creating the order itself.

**First, here's what integrating might look like without an SDK:**

```typescript
const fetch = require('node-fetch');

const apiKey = 'your_api_key';
const baseUrl = 'https://api.ecommerce.com/v1';
const headers = {
  'Authorization': `Bearer ${apiKey}`,
  'Content-Type': 'application/json'
};

const productName = 'Awesome Widget';
const customer = {
  firstName: 'John',
  lastName: 'Doe',
  email: 'john.doe@example.com'
};
const quantity = 2;

async function placeOrder(productName, customer, quantity) {
  try {
    // Step 1: Get product information
    const productResponse = await fetch(`${baseUrl}/products`, { headers });

    if (productResponse.status !== 200) {
      throw new Error(`Could not fetch products. Status code: ${productResponse.status}`);
    }

    const productData = await productResponse.json();
    const product = productData.products.find(p => p.name === productName);

    if (!product) {
      throw new Error(`Product '${productName}' not found.`);
    }

    // Step 2: Create a new customer
    const customerResponse = await fetch(`${baseUrl}/customers`, {
      method: 'POST',
      headers,
      body: JSON.stringify({ customer })
    });

    if (customerResponse.status !== 201) {
      throw new Error(`Could not create customer. Status code: ${customerResponse.status}`);
    }

    const customerData = await customerResponse.json();
    const customerId = customerData.customer.id;

    // Step 3: Place the order
    const orderResponse = await fetch(`${baseUrl}/orders`, {
      method: 'POST',
      headers,
      body: JSON.stringify({
        order: {
          customerId,
          items: [
            {
              productId: product.id,
              quantity
            }
          ]
        }
      })
    });

    if (orderResponse.status !== 201) {
      throw new Error(`Could not place order. Status code: ${orderResponse.status}`);
    }

    console.log('Order placed successfully!');
  } catch (error) {
    console.error(`Error: ${error.message}`);
  }
}

placeOrder(productName, customer, quantity);
```

Note that the API consumer would need to construct all this code themself. They would need to refer to the API documentation to figure out which APIs should be called, what the response data structures look like, which data needs to be extracted, how to handle auth, what error cases might arise and how to handle them.

**What You Manage Manually:**
- Constructing requests and headers  
- Parsing responses  
- Handling errors for each call  
- Managing authentication  
- Sequencing the calls to ensure proper workflow

**Now here's the SDK version of this code. Using an SDK, the same functionality can be achieved with much greater ease:**

```typescript
const { EcommerceClient } = require('ecommerce-sdk');

const apiKey = 'your_api_key';
const client = new EcommerceClient(apiKey);

const productName = 'Awesome Widget';
const customer = {
  firstName: 'John',
  lastName: 'Doe',
  email: 'john.doe@example.com'
};
const quantity = 2;

async function placeOrder(productName, customer, quantity) {
  try {
    await client.placeOrder(productName, customer, quantity);
    console.log('Order placed successfully!');
  } catch (error) {
    console.error(`Error: ${error.message}`);
  }
}

placeOrder(productName, customer, quantity);
```

Notice how much simpler and concise it is. Authentication is handled automatically with the developer just needing to copy in their key. Pre-built functions mean the developer doesn't need to parse through pages of API docs to stitch together the required calls and associated data extraction themselves. Error handling and retries are built-in.

Overall, a far easier and superior experience.

**Advantages of Using an SDK:**
- **Dramatically Reduced Code Complexity**: Fewer lines of code and clearer logic flow  
- **Automatic Authentication and Error Handling**: The SDK's internal routines handle retries, rate limits, and token refreshes  
- **Built-in Best Practices**: Consistent data structures and naming conventions  
- **Faster Onboarding**: Less time spent referencing raw API docs

---

## What's the difference between SDKs and APIs?
APIs and SDKs serve distinct yet complementary roles in software development. **APIs** provide the underlying communication protocols and offer broad flexibility, while **SDKs** wrap these protocols with ready-to-use libraries and best practices that make development faster and more consistent. In summary, APIs & SDKs are symbiotic. Let's talk about coffee to draw the analogy better.

You can think of APIs as the fundamental, bare metal interfaces that enable applications or services to communicate. In our analogous example, APIs are like going to a coffee shop and getting a bag of beans, a grinder, a scale, filter paper, a coffemaker/brewer, kettle, and an instruction guide. Good luck making a delicious brew!

SDKs on the other hand are critical to enabling APIs to reach their full potential, by providing a rapid, ergonomic way to access the API's underlying functionality. In our coffee example, SDKs are more akin to telling a skilled barista “I'd like a latte please”. The barista does all of the work of assembling the ingredients, and you get to focus on the end result.

## API and SDK best practices

Now we know what APIs and SDKs do, what should you keep in mind as you're building them, to ensure they fulfill the promises we've outlined above?

Here are some “gotchas!” to watch out for when building awesome APIs:

- **Design carefully:** It can be extremely difficult to get users to change how they use an API once it's in production. Avoiding unnecessary breaking changes, where possible, will save you many headaches and irate users later.
- **Documentation:** In addition to an “API reference” that details every endpoint and response, consider creating a “usage guide” that walks users through how to use APIs in sequence to accomplish certain tasks.
- **Authentication:** Creating and sending users API keys manually works fine for an MVP, but has obvious security and scalability challenges. An ideal solution is to offer a self-service experience where end-users can generate and revoke keys themselves. For more on API auth, [check out our guide](/post/api-auth-guide).
- **Troubleshooting and support:** Users will inevitably run into issues. It's easy for members of the team to quickly get inundated with support requests. Try to provide self-service tools for troubleshooting API issues, such as logging and monitoring, and community support channels.

Building great SDKs presents a different set of considerations. Keep these in mind if you want to offer a great SDK to your users:

- **How stable is the underlying API?** If the API is undergoing frequent changes, it might be particularly challenging to manually keep the SDKs up-to-date and in sync with the API.
- **Creation and maintenance cost:** Creating native language SDKs for all your customers' preferred languages can be a huge hiring and skills challenge. Each language SDK also has to be updated every time the API changes – ideally in lockstep to avoid the SDK and API being out of sync. This is time-consuming and costly. Many companies have deprecated or scaled back their SDKs after misjudging the work required.
- **Testing and validation:** Plan for thorough testing of the SDKs across different platforms and languages, including unit tests, integration tests, and end-to-end tests, to ensure the SDKs are reliable and compatible with the API.
- **Documentation:** Provide clear examples and code snippets in each language to make the SDKs easy to use and understand.
---

## Simplify SDK Generation with Speakeasy

While the benefits of providing SDKs are clear, creating and maintaining them across multiple languages can be a significant undertaking. It requires specialized skills, substantial development time, and ongoing effort to keep SDKs in sync with API changes. This is where Speakeasy comes in.

Speakeasy is a platform that **automatically generates high-quality, idiomatic SDKs** from your API specification. Our solution helps you:

*   **Reduce Development Time and Costs:** Eliminate the need to manually write and maintain SDKs. Speakeasy handles the heavy lifting, freeing up your team to focus on core product development.
*   **Ensure SDK Quality and Consistency:** Our generated SDKs are built to follow industry best practices. Speakeasy offers comprehensive, automated testing, ensuring reliability and a consistent developer experience across all supported languages. Each generated SDK comes with:
    *   **Comprehensive Test Coverage:** We provide a wide range of tests, including unit, integration, and end-to-end tests, to validate every aspect of the SDK's functionality.
    *   **Automated Test Execution:** Our platform automatically runs these tests whenever your API specification changes, providing immediate feedback on any potential issues.
*   **Keep SDKs in Sync with API Changes:** Speakeasy automatically regenerates your SDKs whenever your API specification is updated, guaranteeing that your SDKs are always up-to-date.
*   **Improve Developer Experience:** Provide developers with easy-to-use, well-documented SDKs that accelerate integration and enhance their overall experience. Each generated SDK comes with extensive, ready-to-publish documentation:
    *   **Interactive Code Examples:** Developers can see real code examples in their preferred language, making it easier to get started.
    *   **Clear and Concise Explanations:** Our documentation is designed to be easy to understand, even for complex API interactions.
    *   **Automatically Updated:** Documentation is regenerated alongside the SDKs, ensuring consistency and accuracy.
*   **API Insights:** Speakeasy provides detailed insights into your API's usage and performance. Our platform helps you track key metrics, identify areas for improvement, and ensure the reliability of your API.

**How it Works:**

1.  **Provide Your API Specification:** Share your OpenAPI or other supported API specification with Speakeasy.
2.  **Configure Your SDKs:** Select the languages you want to support and customize the look and feel of your SDKs, including configuring authentication methods.
3.  **Generate and Publish:** Speakeasy automatically generates your SDKs, runs comprehensive tests, creates detailed documentation, and makes them available for download or through package managers.

Stop spending valuable time and resources on manual SDK development. Let Speakeasy handle the complexities of SDK generation, testing, and documentation so you can focus on building great APIs and delivering exceptional developer experiences. [Learn more about Speakeasy's SDK generation platform](https://www.speakeasy.com/docs/introduction).

**Get started today, [book a demo with us](https://www.speakeasy.com/book-demo).**