What Are PWAs (Progressive Web Apps)?

Shilpa Prabhudesai

Software and web development are continuously evolving, and new paradigms emerge almost every day. These paradigms bridge the gap between traditional web experiences and native mobile applications. One of the most promising is the Progressive Web App (PWA).

A PWA is a website that offers the user an experience of a native mobile app with a unique URL. It can also function as a native application on a mobile device. PWA has become a major talking point in today’s technology landscape.

In this article, we will discuss PWAs in detail, including how they work, their key features and benefits, challenges, and how they are shaping the future of mobile web.

PWAs Explained – What is a PWA?

A PWA is a type of application software delivered through the web that combines the best of web and native apps. It is built using standard web technologies, including HTML, CSS, and JavaScript. A PWA is intended to work on any platform, just like any native application that uses a standards-compliant browser.

PWAs are essentially websites that behave like mobile native applications, offering features such as device installation, offline access, and push notifications. The term “Progressive” in PWA indicates that the application improves over time with the advancement in the user’s device and browser capabilities.

A PWA, once installed, looks like any other app, specifically:

• It has an icon on the home screen, app launcher, launchpad, or start menu.
• PWA appears when it is searched on the device.
• PWA opens in a standalone window, separated from a browser’s user interface.
• It has access to higher levels of integration with the OS, such as URL handling or title bar customization.
• PWA works offline.

Key Characteristics of PWAs

PWAs are defined by the following core characteristics:

• Progressive: PWAs are built with progressive enhancement as a core principle. They work for every user, irrespective of browser choice.
• Responsive: The PWA app can be used on any device, whether desktop, mobile, tablet, or other.
• Connectivity-independent: These applications are powered by service workers, so they work offline or on low-quality networks, as the content and resources are cached using service workers.
• App-like: PWAs provide a user experience that closely resembles that of a native app, with features like a dedicated icon on the home screen, full-screen mode, and offline functionality.
• Fresh: PWAs are always up-to-date with the help of the service worker update process.
• Safe: PWAs are served via HTTPS, which prevents snooping and ensures content hasn’t been tampered with.
• Discoverable: Using W3C manifests and service worker registration, PWAs can be identified as “applications” on search engines.
• Re-engageable: It keeps users engaged using features like push notifications.
• Installable: PWAs can be installed on any user device and can be kept on the home screen instead of app stores.
• Linkable: No need for complex installation, as PWAs can easily be shared via URL.

PWA Architecture

PWAs are built using three main components, explained below:

1. Service Workers

A service worker is a script run in the background by the browser. It is separate from the web page and has features that do not need a web page or user interaction. Some of these features are:

• Background sync
• Push notifications
• Offline functionality (via caching)

This is a JavaScript file that acts as a proxy between the browser and the network. It intercepts network requests and responds with a cached resource, helping users interact with the app even without a stable connection or even offline.

Service workers improve the reliability and performance of PWAs by managing network requests and providing offline access.

2. Web App Manifest

This is a JSON file that contains metadata about the app, such as its name, icons, theme colors, start URL, etc. Using this file, users can install the app on their device like a native app and launch it from their home screen.

Web App Manifest allows developers to customize the app’s appearance and behavior, ensuring a native-like experience.

3. HTTPS

PWAs must be served over HTTPS to ensure security and prevent snooping. HTTPS protects the integrity and confidentiality of data between the user’s device and the site.

HTTPS additionally ensures that all communications between the browser and the server are encrypted, thus protecting user data and enhancing security.

How Does a Progressive Web App Work?

As mentioned, PWAs combine the best features of web and mobile apps to deliver a seamless user experience. Here is a detailed explanation of how PWAs work:

1. Initial Load and Installation

When a user clicks a PWA-enabled website, it loads normally like any other website. The Web App Manifest allows users to install the app onto the device’s home screen. The installation does not download the file from the app store; instead, it creates a shortcut for the app and caches essential resources.

2. Caching and Offline Functionality

Service Worker is registered during the initial visit and installed in the background. It plays a crucial role in enabling offline functionality by pre-caching the key resources like HTML, CSS, JavaScript, and images.

When the PWA is accessed again, the Service Worker serves the cached resources, ensuring faster load times and offline access.

3. Handling Network Requests

Service Workers determine whether to serve a cached version or fetch it from the network. They first intercept the network requests from PWA. This handling of network requests by Service Workers reduces the app’s reliance on network connectivity.

The Service Worker updates the cached resources with the latest versions if network connectivity is available.

4. Push Notifications and Background Sync

PWAs re-engage users and provide timely updates through push notifications. Service Workers handle these even when the PWA is not actively running. PWAs can also perform background synchronization, ensuring that offline actions are synchronized with the server once network connectivity is available. This provides seamless interaction regardless of connectivity and enhances user experience.

Benefits of Progressive Web Apps (PWAs)

PWAs have various benefits, providing a mobile-like experience while retaining the benefits of a website. Some of them are listed below:

• Cross-Platform Compatibility: Built with standard web technologies, PWAs are inherently cross-platform. They can work seamlessly across Windows, macOS, Linux, Android, and iOS, reducing development time and cost.
• Offline Functionality: PWAs’ Service Workers cache data and content, allowing the application to function even when offline or with poor network connectivity.
• App-Like Experience: PWAs behave like native apps with smooth navigation, full-screen interfaces, and the ability to install on home screens.
• Push Notifications: PWAs send push notifications even when the browser is closed, helping developers increase retention and user engagement like mobile apps.
• No App Store Dependency: PWAs need not be installed through the app store. They can be directly installed from the browser. This means:
  • No need to wait for app store approvals
  • Faster update cycles
  • Reduced costs and commissions
• Lightweight and Fast: PWAs are smaller in size than native apps, leading to quicker load times and reduced data usage. This is a desirable feature in bandwidth-constrained environments.
• Automatic Background Sync: PWAs do not require manual updates. Updates made to the website are automatically synced with the PWA. Thus, there is always the latest version of PWA with the latest features and a simple refresh.
• Search Engine Optimization (SEO): PWAs are essentially websites, and hence, they can use SEO techniques like indexing to reach a wider audience, thus enhancing engagement and visibility.

Real-World Examples of PWAs

Many major organizations have adopted PWAs to improve their user experiences. Some of the examples are:

• Twitter Lite: This is Twitter’s PWA that loads quickly, uses less data, and provides offline access, leading to a 65% increase in pages per session and a 75% increase in Tweets sent.
• Pinterest: This website saw a 60% rise in core engagement and a 44% jump in user-generated ad revenue after shifting to PWA.
• Starbucks: This is less than 1% the size of the native iOS app and offers a smooth ordering experience even offline.
• Uber: The Uber PWA is optimized for quick rides on low-speed networks, with the core app taking only 50kB to load.

PWA vs. Native Apps vs. Traditional Web Apps

The following table summarizes the differences between PWA, native apps, and traditional web apps.

Use Cases for PWAs

PWAs are best suited for the following applications:

• Content platforms (news, blogs, media)
• E-commerce websites
• Social media networks
• Educational tools
• Productivity apps
• Small and mid-sized businesses
• Internal enterprise applications

PWAs are an ideal solution for startups or organizations that need fast deployment across multiple platforms with limited resources.

PWA Challenges and Limitations

While PWAs offer numerous benefits, there are still some challenges:

• Platform Limitations:
  • iOS Limitations: There is limited support for background sync and push notifications for PWAs on iOS.
  • App Store Visibility: PWAs do not get identified in app stores unless packaged via tools like Trusted Web Activity (Android) or PWABuilder.
• Hardware Integration: Device features like Bluetooth, NFC, or advanced sensors have limited access through PWA compared to native apps. However, the Web Bluetooth, WebUSB, and WebNFC APIs have helped to bridge this gap.
• Browser Support: Although all major browsers support PWAs, advanced features like file system access and background sync have limited support in some browsers.
• User Perception: Some users may not be as familiar with PWAs as traditional app store apps.

Tools and Frameworks for Building PWAs

The following table provides details of tools and frameworks available for building PWAs:

Once your PWA is ready, you can use various types of tests to verify its quality.

The Future of PWAs

The line between web and native is blurring with increasing browser support and growing adoption by major organizations. PWAs are rapidly becoming popular, especially for cross-platform app development. Some of the future trends include:

• Enhanced Web APIs (e.g., file system access, background sync).
• Better integration of PWAs into app stores like Google Play and Microsoft Store.
• Deeper OS-level integration for notifications, file handling, and sharing.
• Wider enterprise adoption as organizations seek cost-effective, scalable solutions.

Conclusion

By combining the strengths of native and web apps, PWAs offer a flexible, powerful, and cost-effective solution to build and distribute applications. Understanding and adopting PWAs can offer a significant edge in the digital landscape, irrespective of whether you are a developer, business owner, or tech enthusiast.

Major tech companies across the globe are embracing PWAs, overcoming challenges such as optimizing user experience and slow networks. This results in higher conversion rates and improved SEO performance. PWAs effectively bridge the gap between web and mobile apps, providing a superior user experience and advanced functionalities.

In a world where user expectations continue to rise and device ecosystems remain fragmented, PWAs offer a progressive, practical, and robust solution.