Mobile Development•Monday, January 12, 2026

Progressive Web App from Scratch: A Developer's Guide

Braine Agency
Progressive Web App from Scratch: A Developer's Guide

Progressive Web App from Scratch: A Developer's Guide

```html PWA from Scratch: A Developer's Guide | Braine Agency

In today's mobile-first world, user experience is paramount. Progressive Web Apps (PWAs) offer a compelling solution, bridging the gap between native apps and traditional websites. At Braine Agency, we've helped countless businesses leverage the power of PWAs to enhance engagement, improve performance, and reach a wider audience. This guide will walk you through building a PWA from scratch, equipping you with the knowledge and tools to create a modern web application that rivals native app functionality.

What is a Progressive Web App (PWA)?

A Progressive Web App (PWA) is a website that uses modern web capabilities to deliver an app-like experience to users. They are reliable, fast, and engaging, offering benefits that traditional websites simply can't match. Think of it as the best of both worlds – the discoverability of the web combined with the rich functionality of native apps.

Key characteristics of PWAs:

  • Progressive: Works for every user, regardless of browser choice, because they're built with progressive enhancement as a core tenet.
  • Responsive: Fit any form factor: desktop, mobile, tablet, or whatever is next.
  • Connectivity independent: Enhanced with service workers to work offline or on low-quality networks.
  • App-like: Feel like an app to the user with app-style interactions and navigation.
  • Fresh: Always up-to-date thanks to the service worker update process.
  • Safe: Served via HTTPS to prevent snooping and ensure content hasn't been tampered with.
  • Discoverable: Are identifiable as "applications" thanks to W3C manifests and service worker registration scope, allowing search engines to find them.
  • Re-engageable: Make re-engagement easy through features like push notifications.
  • Installable: Allow users to "install" them on their home screen without the hassle of an app store.
  • Linkable: Easily share via URL and don't require complex installation.

According to a Google study, PWAs see a 50% increase in user engagement compared to traditional websites. Furthermore, they can load up to 10x faster, leading to improved conversion rates and a better overall user experience.

Why Build a PWA?

Investing in a PWA can bring significant benefits to your business. Here are some key advantages:

  • Improved User Experience: Faster loading times, offline access, and app-like features create a more engaging experience.
  • Increased Engagement: Push notifications and home screen installation drive repeat visits and user interaction.
  • Broader Reach: PWAs work on any device with a web browser, eliminating the need for separate iOS and Android apps.
  • Reduced Development Costs: Building and maintaining a single PWA can be more cost-effective than developing native apps for multiple platforms.
  • Enhanced SEO: PWAs are easily discoverable by search engines, improving organic visibility.
  • Higher Conversion Rates: A faster, more engaging experience leads to increased conversions and sales.

For example, after switching to a PWA, Twitter Lite saw a 65% increase in pages per session, a 75% increase in Tweets sent, and a 20% decrease in bounce rate. These are the kinds of results Braine Agency strives to achieve for our clients.

Building Your PWA: A Step-by-Step Guide

Now, let's dive into the practical steps of building a PWA from scratch. We'll cover the essential components and provide code examples to guide you through the process.

1. Setting Up Your Project

First, create a new directory for your project and initialize it with a package manager like npm or yarn:


        mkdir my-pwa
        cd my-pwa
        npm init -y

This command creates a `package.json` file, which will manage your project's dependencies.

2. Creating the Basic HTML Structure

Start by creating an `index.html` file with the basic HTML structure:


        <!DOCTYPE html>
        <html lang="en">
        <head>
            <meta charset="UTF-8">
            <meta name="viewport" content="width=device-width, initial-scale=1.0">
            <title>My PWA</title>
            <link rel="stylesheet" href="style.css">
            <link rel="manifest" href="manifest.json">
        </head>
        <body>
            <h1>Welcome to My PWA!</h1>
            <p>This is a basic PWA example.</p>
            <script src="app.js"></script>
        </body>
        </html>

Key points:

  • Viewport meta tag: Ensures the app scales correctly on different devices.
  • Stylesheet link: Links to your CSS file for styling.
  • Manifest link: Links to the `manifest.json` file (explained below).
  • Script link: Links to your JavaScript file for application logic.

Create an empty `style.css` and `app.js` file in the same directory.

3. Creating the Manifest File (manifest.json)

The manifest file is a JSON file that provides metadata about your PWA, such as its name, icons, and display mode. Create a `manifest.json` file with the following content:


        {
            "name": "My PWA",
            "short_name": "PWA",
            "start_url": ".",
            "display": "standalone",
            "background_color": "#ffffff",
            "theme_color": "#000000",
            "icons": [
                {
                    "src": "icon-192x192.png",
                    "sizes": "192x192",
                    "type": "image/png"
                },
                {
                    "src": "icon-512x512.png",
                    "sizes": "512x512",
                    "type": "image/png"
                }
            ]
        }

Explanation of manifest properties:

  • name: The full name of your PWA.
  • short_name: A shorter name for use on the home screen.
  • start_url: The URL that loads when the app is launched. "." refers to the root directory.
  • display: How the app should be displayed (e.g., `standalone`, `fullscreen`, `minimal-ui`, `browser`). `standalone` removes the browser UI.
  • background_color: The background color of the splash screen.
  • theme_color: The theme color for the app's UI.
  • icons: An array of icons for different device sizes. You'll need to create these icon files (icon-192x192.png, icon-512x512.png) and place them in your project directory. There are many online tools to help you generate these icons from a single source image.

4. Implementing the Service Worker (sw.js)

The service worker is the heart of a PWA. It's a JavaScript file that runs in the background, allowing your app to handle network requests, cache assets, and enable offline functionality. Create a `sw.js` file with the following content:


        const cacheName = 'my-pwa-cache-v1';
        const staticAssets = [
            './',
            './index.html',
            './style.css',
            './app.js',
            './icon-192x192.png',
            './icon-512x512.png'
        ];

        self.addEventListener('install', async event => {
            const cache = await caches.open(cacheName);
            await cache.addAll(staticAssets);
        });

        self.addEventListener('fetch', event => {
            event.respondWith(
                caches.match(event.request)
                    .then(response => {
                        return response || fetch(event.request);
                    })
            );
        });

        self.addEventListener('activate', event => {
            event.waitUntil(
                caches.keys().then(cacheNames => {
                    return Promise.all(
                        cacheNames.filter(cache => cache !== cacheName)
                            .map(cache => caches.delete(cache))
                    );
                })
            );
        });

Explanation of the service worker code:

  1. `cacheName` and `staticAssets`: Define the cache name and the list of static assets to cache (HTML, CSS, JavaScript, images).
  2. `install` event: This event is triggered when the service worker is installed. It opens the cache and adds all the static assets to it. `event.waitUntil()` ensures the service worker doesn't become active until the caching is complete.
  3. `fetch` event: This event is triggered every time the browser makes a network request. It checks if the requested resource is in the cache. If it is, it returns the cached version. Otherwise, it fetches the resource from the network.
  4. `activate` event: This event is triggered when the service worker becomes active. It cleans up any old caches. This is important to ensure that users always get the latest version of your app.

5. Registering the Service Worker

Finally, you need to register the service worker in your `app.js` file:


        if ('serviceWorker' in navigator) {
            window.addEventListener('load', () => {
                navigator.serviceWorker.register('/sw.js')
                    .then(registration => {
                        console.log('Service Worker registered with scope:', registration.scope);
                    })
                    .catch(error => {
                        console.error('Service Worker registration failed:', error);
                    });
            });
        }

This code checks if the browser supports service workers. If it does, it registers the `sw.js` file when the page loads. The `scope` defines which URLs the service worker controls.

6. Testing Your PWA

To test your PWA, you'll need to serve it over HTTPS. You can use a local development server like `http-server` or `live-server`:


        npm install -g http-server
        http-server

Open your browser and navigate to the URL provided by the server (usually `http://localhost:8080`). Use your browser's developer tools (usually by pressing F12) to inspect the "Application" or "Service Workers" tab. You should see that your service worker is registered and running. You can also simulate offline mode to test the offline functionality of your PWA.

Enhancing Your PWA: Advanced Features

Once you have a basic PWA up and running, you can enhance it with advanced features like push notifications and background sync.

Push Notifications

Push notifications allow you to re-engage users with timely and relevant updates. Implementing push notifications requires a backend server to manage subscriptions and send notifications. This is a more complex topic that deserves its own dedicated guide, but here's a high-level overview:

  1. Request Permission: Ask the user for permission to send push notifications.
  2. Subscribe to Notifications: Get a unique subscription endpoint from the push service (e.g., Firebase Cloud Messaging).
  3. Send Notifications: Use your backend server to send notifications to the subscription endpoint.
  4. Handle Notifications: Use the service worker to handle incoming notifications and display them to the user.

Background Sync

Background sync allows your PWA to perform tasks in the background, even when the user is offline. This is useful for tasks like submitting forms or uploading files. Here's the basic process:

  1. Register for Sync: Use the `SyncManager` API to register for a background sync event.
  2. Handle Sync Event: In your service worker, listen for the sync event and perform the desired task.

Best Practices for PWA Development

To ensure your PWA is successful, follow these best practices:

  • Prioritize Performance: Optimize your code and assets for fast loading times. Use tools like Lighthouse to identify performance bottlenecks.
  • Implement Offline Functionality: Cache static assets and consider caching dynamic data to provide a seamless offline experience.
  • Ensure Accessibility: Make your PWA accessible to users with disabilities by following accessibility guidelines.
  • Use HTTPS: Serve your PWA over HTTPS to ensure security and data integrity.
  • Test Thoroughly: Test your PWA on different devices and browsers to ensure compatibility and a consistent user experience.
  • Keep it Updated: Regularly update your PWA with new features and bug fixes.

Use Cases for PWAs

PWAs are suitable for a wide range of applications. Here are some common use cases:

  • E-commerce: Improve the shopping experience with faster loading times, offline browsing, and push notifications for promotions and order updates.
  • News and Media: Deliver news articles and multimedia content quickly and reliably, even on low-bandwidth connections.
  • Social Media: Provide a fast and engaging social media experience with offline access to cached content and push notifications for new posts and updates.
  • Travel and Tourism: Offer offline access to travel information, maps, and booking details.
  • Productivity Tools: Create offline-capable productivity apps for note-taking, task management, and document editing.

For instance, Starbucks uses a PWA to provide a seamless ordering experience, even when users have poor network connectivity. This has resulted in a significant increase in mobile orders and customer satisfaction.

Conclusion: Embrace the Power of PWAs

Progressive Web Apps are revolutionizing the way we experience the web. By combining the best of web and native app technologies, PWAs offer a compelling solution for businesses looking to enhance user engagement, improve performance, and reach a wider audience. This guide has provided you with a comprehensive overview of building a PWA from scratch, covering the essential components and best practices.

Ready to transform your web presence with a powerful PWA? Contact Braine Agency today for a free consultation! Our experienced team of developers can help you design, build, and deploy a PWA that meets your specific business needs and delivers exceptional results. Let us help you unlock the full potential of PWAs and take your business to the next level.

Get in touch with Braine Agency

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