PWA vs. SPA, or How to Choose Web Development Architectures

When it comes to developing apps, it's all about user experience (UX) and mobile these days. Users want websites and apps to be responsive and accessible on any device. New web app architectures and technologies, which mimic native apps, have been developed to meet these demands,.

Constantly evolving frameworks bring improvements to the web app development process. The choice of tech has a big impact on the project's future development, so it's important to take a responsible approach and understand future goals.

Single page applications (SPAs) and progressive web applications (PWAs) are on the minds of those thinking about building their application. These two architectures are worth considering and choosing between. Therefore, the main goals of this article are to compare PWA vs SPA and help you select one of the architectures.

What is a Progressive Web App (PWA)?

Progressive Web Apps (or PWAs) are web applications that leverage modern capabilities to provide users with a native application-style experience. PWAs offer a robust and interactive experience that improves over time with automatic updates.

PWA applications are built using standard web technologies, including HTML, CSS, and JavaScript. Service workers and manifest allow applications to run offline and load instantly.

PWA Key Features

There are everal key features and benefits of the PWA:

• Service workers enable PWAs to dash offline or on low-quality networks by caching APP files using minification, code separation, and compression. This reduces initial application load time and improves overall performance.
• Progressive web app architecture also uses a single code base, making the Web app available on any device without building different versions.
• PWAs can use the Notifications API to send push notifications to users, whether the app is open or in the background.
• With PWAs, you can install automatic updates without requiring the user to update the app from the App Store manually. The new version automatically downloads in the background when you update a PWA.
• These applications work over HTTPS, which prevents eavesdropping and ensures that content has not been tampered with during transmission. In addition, using HTML, CSS, and JavaScript makes creating applications on a small budget possible.
• PWA can appear in the search engine; you don't need to download it from the App Store. So the user can easily install it and access it through a web shortcut on the device.

Like any technology, PWAs have their drawbacks. Web applications can have many features that help accomplish various tasks and processes. However, because progressive web applications are lightweight, they have limited features that users can take advantage of.

With PWAs, you can achieve good results in terms of performance, but this metric of native applications is still much higher than that of PWAs.

Components of PWA

A vital part of the PWA architecture is using a service worker to cache assets and handle fetch requests, as well as the web application manifest file. These components work together to deliver a native experience.

Service worker

When a PWA application is installed, it registers a service worker file that controls all subsequent online and offline visits to the application.

It caches static assets and dependencies so that the progressive web app loads instantly, much like native applications. The Cache API can store critical application shell files, static assets, API endpoints, and more to serve data offline.

When the user is offline or on a low-quality network, the service worker can serve cached content instead of fetching it from the network each time. This provides a convenient offline experience and improves overall performance for the user.

WebAssembly

WebAssembly lets you run precompiled code in a web browser at near-native speed. WebAssembly modules are compiled into a binary format that modern browsers can execute, which gives you a big performance boost over traditional JavaScript code. You can run it on multiple platforms and devices, including desktops, laptops, mobile phones, and even embedded systems.

WebAssembly also allows developers to integrate external libraries and code written in different programming languages into PWAs.

Manifest file

Running in parallel in PWA is the manifest file, a JSON file containing metadata about the progressive web app. Commonly referred to as manifest.json, it allows you to define

• Display style. Whether you want the PWA to behave like an application, use the entire screen, or be like a web page,
• Shortcuts. The ability to add shortcuts/icons to the mobile or desktop home screen.
• Name. The name and a brief description of the application.
• Orientation. Preferred display orientation - portrait or landscape.
• Theme Color. It sets the default theme color for Chrome tabs, app banners, etc.
• Launch URL. The entry point URL is used to launch the app from shortcuts.

So, to summarize, the manifest file allows the PWA to display, access, and behave like a standard installed application.

PWA Development Tools

To create a progressive web application, you can use the following tools:

1. Ionic is built on the modern Apache Cordova technology stack and the Angular.js framework. It has a vast library of Android and iOS components that developers can use to create web pages that run in the device's browser using WebView. This is the main advantage of Ionic for PWA development.
2. Polymer is an open-source progressive web app architecture framework developed by Google. It consists of a wide range of templates, tools for building progressive web applications, and web components that simplify the entire PWA development process.
3. AngularJS is one of the most popular frameworks for developing progressive web applications due to the availability of necessary tools, extensive community, and a particular way of implementing the application.
4. Vue.js is used to create PWAs due to its ease of coding and high rendering speed. It allows you to scale a progressive web app with the help of additional packages.

As an option, you can also use testing tools to validate functionality and regressions, audit tools to assess the readiness and performance of the PWA, and much more.

PWA Use Cases

You can also understand this web development architecture through real-world PWA use cases:

• The lightweight PWA version of Twitter Lite (currently X) is designed for users in regions with limited Internet access. It features fast load times, offline access, and push notifications.
• Uber's web app was redesigned entirely in PWA to ensure the checkout process was identical to the native mobile app.
• Starbucks' PWA provides a mobile-friendly ordering experience, allowing customers to order, pay, and receive rewards without downloading the app.

By harnessing the power of PWAs, you can deliver an experience that maintains native app-level usability and functionality to a broad audience across multiple devices and platforms.

PWA Challenges

Despite their cross-platform availability, progressive web apps only work on iOS 11.3 and above, and encounter many technical glitches when running in Safari and Firefox.

It's also worth noting that PWAs lack access to some device features: for example, Bluetooth, the camera, and the phone's memory cannot be used by PWAs, unlike mobile apps. As a result, PWAs cannot implement a number of features that are available to mobile apps.

In addition, even developers cannot take full advantage of the device's capabilities with progressive web applications. Despite being an important requirement for most applications, the clipboard or file system is not available in PWAs. And when developers don't have access to the right tools, PWA development becomes even more challenging.

There are also some security concerns. Because PWAs are downloaded from unknown sources, the security and privacy concerns associated with PWAs are legitimate, and your users will definitely receive a download security warning.

Typically, browsers such as Google Chrome can automatically correct HTML syntax without inconveniencing developers or users. However, this doesn't always work for JavaScript errors. As a result, JavaScript errors can prevent search engines from crawling and indexing your progressive web application.

What is a Single Page Application (SPA)?

Single Page Applications (or SPAs) are web applications that load a single HTML page and update it dynamically as the user interacts with the application rather than loading entire new pages.

SPA applications rely on JavaScript for client-side routing rather than a full page refresh in the browser. Popular frameworks such as React, Angular, and Vue.js are used to create complex SPAs. By reducing page loads, SPAs improve performance and allow smoother interaction with applications.

Here are the key features of single page application architecture:

• SPAs display the user interface on the client, not the server. All navigation takes place within a single HTML page. This avoids a complete reload of the page.
• By changing the URL string without reloading, SPAs provide application-like interactivity by dynamically updating content.
• By caching JavaScript and other assets, SPAs can support primary offline usage.
• Frameworks such as React and Angular include build systems that simplify dependency management and bundled code deployment.
• By reducing the total page load, SPAs provide fast initial load times and high performance when transitioning between routes.

Although SPAs provide fast and responsive user interaction once downloaded, their initial load time can be longer than that of traditional sites. This is because the entire application and its resources must be downloaded first. Such a feature can be a significant drawback for users with slow Internet connections.

Because SPA architectures display only one page, they are difficult to optimize for search engines, which rank based on the number of pages and content.

If not properly secured, SPAs can also be vulnerable to specific security issues, such as cross-site scripting (XSS) attacks.

Components of SPA

SPAs use a client-side architecture in which the vast majority of the application logic and data processing takes place in the user's browser.

• A single HTML page. SPAs initially load a single HTML page and dynamically update its content using JavaScript as the user interacts with the application.
• Client-side routing. SPAs use client-side routing to control navigation between different views or sections of the application without reloading the entire page.
• Data retrieval and management. SPAs use JavaScript, Asynchronous JavaScript, and XML (AJAX) to retrieve data from the server asynchronously without refreshing the page.
• State management. SPAs manage application state (e.g., user input, data, and UI state) using various techniques such as Redux, Vuex, or proprietary state management solutions.

SPAs work with data dynamically, retrieving it from the server using AJAX requests. The retrieved data is stored in the application state management system, ensuring its immutability and availability throughout the application.

As a user interacts with the SPA, the state management system updates the application state to reflect the changes made by the user. This approach provides a smooth and responsive experience by allowing the application to respond to user actions without reloading the page.

Tools for SPA Development

Here are some frameworks you can use to create your own single page web application:

1. Angular. This framework from Google provides a structured approach to building SPAs, including features such as two-way data binding, dependency injection, and a command-line interface for building projects.
2. React. Its component-based architecture, virtual DOM, and strong community support make it an excellent choice for building a single page application. React's flexibility makes it easy to integrate with other libraries and frameworks.
3. Aurelia. This framework offers two-way data binding, a convenient routing system, and a customizable architecture. Aurelia's modular codebase makes it an excellent choice for building single page applications.
4. Ember.js. The framework comes with built-in tools and practices that make it easy to create complex SPAs. Also handy is Ember's built-in "ember-cli" generator tool for common tasks.

Other options also include Vue.js, Svelte, Mithril, etc.

SPA Application Examples

Here are a few examples of SPA applications:

• Gmail's SPA design provides smooth and responsive email management, dynamic email loading, and smooth navigation between folders.
• As an example of single page application architecture, Trello allows users to create and efficiently manage project boards, cards, and tasks, providing a highly interactive and collaborative experience.
• Netflix offers an easy-to-use SPA interface to access TV set-top boxes and movies with dynamic content downloads and personalized recommendations.

Single page web applications are ideal for creating highly interactive and responsive web resources, especially for delivering dynamic content that requires fast load times.

SPA Challenges

Sites running on single page application architecture will always have problems with search engine optimization. The culprit is the lack of JavaScript in the crawlers of some popular search engines.

Because SPA is a single page, this architecture breaks the browser's design for navigating through the page history using the "forward" and "back" buttons. That is, when the user presses the "back" button to return to the previous screen state in SPA, the single page application is "reset" and the previous page in the browser history is displayed. However, it is possible to work around this problem by changing the hash identifier of the browser's URL fragment to match the current screen state.

Another challenge is working with analytics. Analytics tools, such as Google Analytics, rely heavily on loading complete new pages in the browser.

With SPA, once a page is loaded, all subsequent changes are handled within the application. If the application doesn't call a function to update the analytics package at that point, the browser will never trigger a new page load, nothing will be added to the browser's history, and the analytics package will have no idea who is doing what on the site.

Selection Criteria PWA vs SPA

The choice between PWA and SPA depends on the project's specific business needs and technical requirements. Here are some criteria to guide the choice:

1. Native experience. If you want to build a native app with features like offline access and push notifications but are on a budget, PWA is the right choice.
2. Performance and responsiveness. SPA is a better choice for applications requiring high performance and responsiveness, especially on mobile devices.
3. Device compatibility. If the target audience uses a wide range of devices and browsers, PWA is a better option due to its compatibility with different platforms.
4. Complexity and development time. SPAs can be more complex to develop than traditional PWAs, so technical expertise and available resources should be considered.
5. Business objectives. Specific business goals, objectives, and user needs should ultimately determine the choice between PWAs and SPAs.

In general, you can evaluate the functionality of PWA and SPA not only through the descriptions in our article but also by using web applications that are available almost everywhere. This will allow you to decide on the architecture for your application.

PWA vs SPA Comparison

Let's compare PWA vs SPA on a number of criteria, including search engine optimization, download speed, user accessibility, and complexity of development.

The choice between PWA and SPA depends on the specific project requirements. PWA is the better choice for native app-like experiences and offline accessibility. SPA is the better choice for highly interactive and responsive web applications.

A Few Words About MPA

It is also worth mentioning the existence of multi-page apps since we touched on the topic of single page apps.

Multi-page applications (or MPAs) are websites with multiple linked pages, each with a separate HTML file. As users browse these sites, they download new pages from the server.

Multi-page applications have improved visibility in search engines, which helps companies attract more traffic. MPAs are suitable for large applications that handle large amounts of content and traffic.

In comparison, single page application architecture loads all pages in advance and updates specific sections of a Web page without refreshing the entire page, creating a smoother and more interactive experience for users. MPAs are inferior to SPAs in terms of loading speed because they contain more content.

Conclusion

In general, PWAs are great because they provide the convenience of native applications, as well as offline availability and improved performance. SPAs are also good because they provide seamless user interaction and dynamic content updates.

Progressive web app architecture offers users more native features, like push notifications and offline support. PWAs are the best choice for search engine optimization (SEO) because search engines index them like regular websites. However, they require more resources and developer expertise to build, and they cost more to maintain and update because they are tied to a back-end server.

A single-page app architecture makes it easier for users because they don't have to refresh the whole page to change content. Single-page apps are easier to develop and may load faster initially, but they may be slower to modernize and more difficult to index by search engines.

The choice between PWA and SPA depends on what you need and what you want for your project. You can figure out which one is better for you by looking at what you can do and what features the two architectures have.