How to Make API Calls in Angular Applications: Complete Guide to Best Practices and Process in 2025

Do you know by 2030, the number of APIs in use will exceed 2 billion, with organizations already using more than 20,000 APIs on average? Today, as an Angular developer, mastering API calls is your bridge to creating real-time, interactive applications that users love.

Angular, with its robust HTTPClient module, makes API integration seamless, allowing you to fetch and manipulate data efficiently. Whether you're working on an Angular project for API integration or troubleshooting data flow issues, understanding the nuances of API calls is critical to your success.

This guide will equip you with the best practices and hands-on techniques to make API calls in Angular, helping you create faster, more dynamic applications.

Let’s get started!

How to Make API Calls in Angular Applications? Step-by-Step Process

APIs, enabling data exchange between front-end interfaces and back-end systems. Understanding API calls in Angular allows you to build dynamic, data-driven applications using methods like GET, POST, PUT, and DELETE. 

Here’s an in-depth explanation of how to make API calls and handle them effectively in Angular.

Setting Up Your Angular Project for API Integration

Before making API calls, setting up a clean Angular environment is essential. Let’s ensure you have all the tools and configurations in place.

1. Install Node.js and npm: Node.js provides the runtime for Angular, and npm (Node Package Manager) allows you to install Angular and other necessary packages. 

Once installed, you can verify the installation with commands like node -v and npm -v to ensure everything works.

node -v
npm -v

2. Install Angular CLI: Angular CLI (Command Line Interface) is a developer tool that simplifies Angular project creation and management. 

You can Install it globally using npm install -g @angular/cli to ensure you are able to create and manage projects efficiently.

npm install -g @angular/cli

3. Create a New Angular Project: Use the CLI command ng new project-name to generate the boilerplate code for a new Angular application. This includes default configurations and files to get started.

ng new my-angular-app

4. Navigate to the Project Directory: Change into the project folder using cd project-name, where you’ll write your application code.

cd my-angular-app

Once you have set up your Angular project for API integration, let’s get into the HttpClient module!

Understanding the HttpClient Module in Angular

The HttpClient module is the backbone of handling API calls in Angular. It’s designed to simplify HTTP communication and handle data streams with observables. Here’s how it is used:

1. Importing HttpClientModule: To use HttpClient, you must import HttpClientModule in the root module (app.module.ts). This enables HTTP services throughout your application.

See how it’s done below:

import { HttpClientModule } from '@angular/common/http';
@NgModule({
  imports: [HttpClientModule],
})
export class AppModule {}

2. Key Concepts:

• Observables: Angular uses observables (from RxJS) to manage asynchronous data streams returned by API calls. These streams emit values over time, making it easier to handle real-time data updates.
• Requests and Responses: The HttpClient module simplifies sending requests and processing responses using easy-to-read methods like get, post, put, and delete.

Now, let's see how you can make the GET requests!

Making GET Requests: Retrieving Data from APIs

GET requests are used to fetch data from a server. You use the get method of HttpClient to make API calls. The data is returned as an observable, which can be subscribed to for handling the response.

Here’s how code snippet for it can be written:

constructor(private http: HttpClient) {}
getData() {
  this.http.get('https://api.example.com/data').subscribe((response) => {
    console.log(response);
  });
}

Code Explanation:

• this.http.get: Sends the GET request to the API endpoint.
• subscribe: Waits for the API’s response and processes it when it arrives.

Now, how do you handle errors while using APIs? See ahead!

Handling API Errors: Best Practices for Error Management

APIs are not foolproof; handling errors gracefully is essential to ensure your application remains user-friendly. For that, the catchError operator is used. It catches errors and processes them before they reach the application’s logic. 

For example, if the server is down, you can display a custom error message as shown in the code snippet below:

getData() {
  this.http.get('https://api.example.com/data').pipe(
    catchError((error) => {
      console.error('Error:', error);
      return throwError(() => new Error('Failed to fetch data'));
    }

The message will be shown as ‘Failed to fetch data.’ This code logs errors and prevents the app from crashing.

The next step is sending information to the APIs!

Making POST Requests: Sending Data to APIs

POST requests send data to an API, such as submitting a form or creating a new record. The payload (data to be sent) is typically formatted as JSON. The server processes the JSON payload, creates a resource, or updates a database.

See how it’s written in below snippet:

const payload = { name: 'John', age: 30 };
this.http.post('https://api.example.com/users', payload).subscribe();

Code Explanation:

• post: Sends data to the API. 
• Payload: The JSON object representing the data to be submitted.

Once you are done with POST requests, files will be uploaded!

Uploading Files in Angular: Working with FormData

File uploads require special handling, which is where FormData comes in. It is a JavaScript object that allows you to append files and other key-value pairs for submission.

Here’s how it's used:

const formData = new FormData();
formData.append('file', file);
this.http.post('https://api.example.com/upload', formData).subscribe();

But why FormData?

• Encodes file data for API compatibility.
• It enables the smooth transmission of binary data (files) alongside regular data fields.

Working with Query Parameters in API Calls

Query parameters refine API responses by enabling features like filtering, sorting, and pagination. To bring in the use of query parameters, you will use the HttpParams class to append query parameters and add parameters to GET requests.

Below is the showcase of implementing HttpParams:

this.http.get('https://api.example.com/items', {
  params: new HttpParams().set('page', '1').set('sort', 'asc'),
}).subscribe();

Query parameters ensure the API returns only the data you need, reducing payload size and improving performance.

The next important step is performance optimization!

Improving Performance: Caching API Responses with Interceptors

Interceptors are middleware components that modify HTTP requests and responses. Caching helps reduce server calls and speeds up your application. 

For that, you create an interceptor to cache responses in the way shown below:

intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
  const cachedResponse = localStorage.getItem(req.url);
  if (cachedResponse) {
    return of(JSON.parse(cachedResponse));
  }
  return next.handle(req).pipe(
    tap((response) => localStorage.setItem(req.url, JSON.stringify(response)))
  );
}

The key benefits of using interceptors include:

• Reduces redundant API calls.
• Enhances user experience.
• Cached responses speed up repeat API calls and reduce server load.

At last, you text your API calls in angular!

Testing API Calls in Angular: Mocking HTTP Requests

Testing ensures your API logic works correctly during development. For this, you use HttpClientTestingModule, which allows you to simulate API calls without hitting a live server, as done below:

TestBed.configureTestingModule({
  imports: [HttpClientTestingModule],
});

Once you import the testing module, mock a GET request and verify the response as shown below:

httpMock.expectOne('https://api.example.com/data').flush(mockData);

There you go! With these step-by-step insights, you’re ready to handle any Angular project for API integration like a pro. 

Also Read: Top 9 Machine Learning APIs for Data Science You Need to Know About

Let’s catch up on its importance in real cases!

Understanding the Importance of API Calls in Angular

What if you use a travel booking app that doesn’t show real-time flight availability or an e-commerce app where product details never update? Sounds frustrating, right? 

This is where API calls come into play, acting as the communication bridge between applications' front and back-end technologies. It ensures your Angular app is interactive, user-friendly, and capable of delivering real-time information.

Let’s look at how API calls power real-world applications, enhancing their functionality and user experience.

Real-World Example 1: Travel Booking App

A travel booking platform relies heavily on APIs to provide users a seamless experience. Angular applications make use of API calls to integrate various services:

• Fetching Flight Details: APIs connect the app to airline servers, retrieving flight schedules, prices, and availability in real time. This allows users to book flights instantly without worrying about outdated information.
• Hotel Information: The app pulls room availability, pricing, photos, and user reviews via hotel APIs. Angular’s data binding ensures this data dynamically updates on the front end.
• Weather Forecasts: APIs fetch weather data from meteorological services, helping users plan trips better by displaying up-to-date forecasts directly within the app.

The next example is e-commerce platforms!

Real-World Example 2: E-commerce Application

E-commerce platforms thrive on providing personalized and efficient shopping experiences, made possible by integrating APIs with Angular apps:

• Retrieving Product Data: APIs pull product details, pricing, availability, and ratings from the backend or external services. Angular dynamically displays this data on category pages or search results.
• User Profiles: APIs fetch user-specific data, like past orders, wishlists, and recommendations. This personalization boosts user engagement and loyalty.
• Managing Shopping Carts: Cart operations like adding items, removing them, or calculating totals are powered by API calls. These interactions ensure real-time updates to the cart view, providing a smoother shopping experience.

Also Read: How to Run the Angular Project [Step-By-Step Explanation]

As you can see, API calls in Angular aren’t just about fetching or sending data — they’re about ensuring your application is responsive, scalable, and user-friendly. 

By mastering API integrations:

• You Build for Scalability: APIs allow Angular apps to handle high user loads by fetching data asynchronously and efficiently.
• You Ensure Real-Time Updates: Dynamic data refresh ensures users see the latest information without needing to refresh pages.
• You Enhance User Experience: Seamless communication between frontend and backend reduces latency and improves functionality.

In short, understanding how API calls work in Angular helps you design applications that perform well and stand out in a competitive market!

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Next, let’s get into some of the best practices while dealing with API calls in Angular!

Best Practices to Follow While Making API Calls in Angular Applications

Making efficient and secure API calls in Angular is key to building high-performing, dynamic applications. For that, you must follow best practices to ensure your code is optimized, secure, and maintainable. 

Here are some of the actionable tips to guide you:

1. Use HttpClient for Simplified API Calls

Angular’s HttpClient module is your go-to tool for making API calls. It simplifies the process with built-in methods and seamlessly integrates with RxJS observables for asynchronous operations.

Tip: Always import HttpClientModule in your root module (app.module.ts).

2. Handle Errors Gracefully

APIs can fail for many reasons — network issues, server errors, or invalid requests. Angular's RxJS operators, like catchError, allow you to manage errors without crashing the app.

Example: Log errors, show user-friendly messages, or retry failed requests using retry.

3. Optimize API Calls

Unnecessary API requests can slow down your app and overload the server. Use strategies like:

• Caching Responses: Save frequently used data locally using interceptors.
• Debouncing Requests: Reduce redundant calls by delaying API requests until user input stabilizes.

4. Consider Using Web Workers

For heavy tasks like processing large datasets or filtering responses, Web Workers can offload operations from the main thread, improving app performance.

Tip: Integrate Web Workers with Angular CLI to handle computational tasks while keeping your UI responsive.

5. Ensure Security

API security is critical for protecting sensitive data. Follow these guidelines:

• Use HTTPS to encrypt API communication.
• Implement authentication mechanisms like OAuth or JWT tokens.
• Avoid exposing sensitive data such as API keys in your Angular app.

6. Test API Calls Thoroughly

Testing ensures your API integrations work as expected. Use HttpClientTestingModule to mock HTTP requests during testing and verify your app’s behavior without hitting live servers.

Tip: Test for both success and failure scenarios to handle edge cases.

7. Stay Updated

Angular regularly introduces new features and performance improvements. Ensure you’re using the latest version of Angular to leverage updates in the HttpClient module, RxJS, and best practices for API integration.

By following these best practices, you can ensure that your API calls in Angular are efficient, secure, and user-friendly!

Also Read: 29 Most Commonly Asked AngularJS Interview Questions and Answers [For Beginners & Experienced]

Conclusion

As an Angular developer, mastering API calls in Angular is a must for creating truly dynamic, data-driven apps. If you’ve been thinking about building or enhancing your skills for your next Angular project for API integration, you don’t have to do it alone. 

upGrad, with its top-notch courses, hands-on projects, and personalized mentorship, equips you with everything you need to excel in Angular development and beyond. Join thousands of learners who have trusted upGrad via:

• Booking a free counseling session to explore career opportunities.
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References: 
https://www.f5.com/resources/infographic/the-biggest-api-security-red-flags