What Is a Single Page Application (SPA)?

Desktop apps are slowly but surely replaced by web applications, which are more convenient to use, easy to upgrade and manage, and are not bound to a single device. 

If you have ever wondered about how the websites you frequently use are built or thought about building one on your own, you most definitely stumbled across the so-called single-page application. 

We’ve gathered the most useful information about SPAs and put it in this article, so if you wish to find out more, let’s dive in.

What is a single-page application?

A single-page application (SPA) is an app that doesn’t reload the page during usage and works inside a browser. In more geek-friendly words, SPAs interact with users by dynamically replacing their content with new data fetched from the web server. As the page refresh never occurs, all necessary JavaScript, HTML, and CSS code is retrieved with a single load or appropriately loaded as needed in response to user actions.

A properly configured SPA delivers an amazing user experience since users can enjoy the natural feel of the app without needing to wait for it to reload.

The origins of single-page applications aren’t clear, but the concept arose sometime in early 2003. Websites like Gmail, Twitter, Facebook, Google Drive, and GitHub are the best real-life examples of SPAs we use every day.

What does the single-page app architecture look like?

Single-page application architecture is pretty simple as it consists of client-side technologies and server-side ones. 

When it comes to site rendering, there are 3 main options you can choose from:

• client-side rendering (CSR) – a great option for simple websites, but keep in mind that it requires more resources from the device and may cause browser overload,
• server-side rendering (SSR) – providing great speed while not overloading the browser,
• static site generators (SSG) – not the best-suited if you have dynamic content on your website.

Single-page apps help to avoid any interruptions in a user’s journey and, by limiting the lag time between pages, the website feels and behaves more like a desktop application.

Since websites have a great deal of repeating content some of it stays the same no matter where the user clicks. Those are sections like headers, footers, logos, and navigation bars. Other content, like filters or banners changes from section to section. But how does that work exactly?

Single-page application in React

React is a JavaScript library developed by Facebook engineers in 2013. It’s used throughout their product range as a base for Facebook, Messenger, WhatsApp, and Instagram. React is a great choice for those just getting started with front-end development and is widely used by startups and companies that value flexibility. It also offers a variety of integration options with other frameworks and technologies.

Single-page application in Angular

Angular is also a JavaScript framework, slightly older than React, created in 2010. It’s based on TypeScript, which makes it an amazing option for large development teams. Among the popular single-page applications built in Angular are Google products, like Gmail and Google Drive.

Single-page vs multiple-page application

Let’s think of a picture of an elephant and a horse that you view on a website. 

A traditional multi-page website will create the entire website on the server and send it to your browser. A SPA will give you more like a paint-by-numbers guide for the website plus the guides you will likely need. 

This means the server sends the components for the SPA to use as well as the raw data and the website decides how to display the pieces and fill the content. In the end in both cases, you will see the exact same picture, but when you filter the results or request new content the speed of a single-page app will be the most noticeable. 

On a traditional website, once you request another animal to show up, the server is going to create the entire site all over again and send it back to you. In a single-page application, the server will send the instructions on how to display a new animal and leave the rest unchanged. By making use of page rendering where websites are dynamically rewritten instead of being reloaded completely, SPAs are a whole lot faster than traditional multi-page applications.

When to use a single-page application?

Building a single-page application is a great idea if you have a business or a personal website that needs a robust platform with a small data volume. It’s also suitable if you plan on developing a native mobile app. 

Apart from that SPAs can be used for:

• SaaS (Software-as-a-Service) platforms as they need to be fast loading and responsive,
• social networks since they are optimized for continuous scrolling,
• closed communities (like customer portals) as they tend to be closed digital communities that only a few people access at once. What is more, they don’t need to be SEO optimized, and the navigation needs to load quickly.

Pros and cons of single-page apps

We’ve already mentioned the main advantage of SPAs which is their speed. This is a result of loading all the resources (HTML, CSS, and JavaScript) at the very launch of the app. 

But that’s not the only reason why people choose to develop single-page applications. Other benefits are:

• a simpler development – with SPAs there’s no need to write code to render pages on the server; the development is much easier to start since you need a file://URI file without the need for having any server,
• easier creation of a mobile app – when building a mobile application, developers can share the same backend code between the web app and the native mobile app,
• easier debugging – single-page apps are easy to debug just by using Chrome,
• effective caching of local storage – since the app sends only one request and then stores the data it can work even offline,
• possible transition to PWA – SPAs make it easier for developers to transform them into progressive web applications, which are useful for mobile device browsing,
• fewer resources used – single-page apps allow data to be cached to be accessed later – this means the content already viewed can be accessed even without an internet connection.

However, it wouldn’t be fair if we didn’t give you some disadvantages of single-page applications as we don’t want to sound biased. Some of those are:

• SEO can be tricky – since in single-page apps the URL doesn’t really change it’s harder for the search engineer to index your website,
• more load on a browser – if your users have low-power devices the speed of the website will be significantly decreased; additionally, you need to make sure that your page doesn’t consume more memory than it actually needs,
• security – due to cross-site scripting (XSS) and since no new pages are loaded, hackers can more easily get into your website.

Benefits of single-page apps for users

Apart from the obvious speed of single-page apps, as we said many times before, from the user perspective SPAs also offer a one-of-a-kind user experience. It’s so-called linear UX, which means the website is easy to navigate and understand, meaning users find exactly what they’re looking for right from the get-go.

Apart from that, single-pagers work amazingly well on mobile devices since all users have to do to navigate the website is scroll up and down.

Benefits of single-page apps for businesses

From the business point of view, SPAs are faster to develop thanks to the shared backend API between the web and mobile app. This influences the information flow, making it more streamlined. 

Considering the great speed of the apps, businesses will most likely get more users interested in their app, which means potentially bigger profits.

Why are single-page applications so trendy?

Research shows that more than half of the web traffic comes from mobile devices. People spend more time on the internet than ever. This means speed and friendly UX have become a necessity. SPAs not only address those needs but are also perfect for MVP development thanks to their simple and responsive design and quick load times.

Well-known examples of single-page apps

Single-page applications are so popular that the majority of us use at least one of them on a daily basis.

Netflix

Surprisingly, a streaming service that’s taking advantage of the SPA approach. With the large quantity of data streamed by a huge number of users, you can definitely tell that Netflix greatly benefits from having a single-page app.

Gmail

Once Gmail loads its data the sidebars and headers stay the same no matter where you go within the app making it a great example of a single-page application.

Facebook

Endless scrolling on Facebook is possible thanks to its single-page capabilities. You don’t need to refresh the page to see new posts as it all loads dynamically. If you turn your airplane mode on or lose the internet connection most of the content will still be visible since it’s cached in your browser.

What is a multi-page application?

To cut the long story short, multi-page apps work more traditionally. Every change in the displayed data or a request sent to the server renders a brand new page. Those apps tend to be larger than SPAs, but they need to be due to the amount of content. 

From the development point of view, multi-page applications are harder to develop and generally consume more time and resources.

Pros and cons of multiple-page apps

MPAs are the best approach for websites that require a more complex few-level navigation. They are also good for SEO purposes as they’re easier to optimize and rank for different keywords. Multiple-page apps are easily scalable as their architecture allows the creation of as many pages as necessary. There are also widely available ready-made solutions (CMS).

On the other hand, a multi-page application is harder to develop. Their frontend and backend are tightly connected, and developers need to use separate frameworks for either client-side or server-side. This means a longer development time, and longer time-to-market. You also have to take into consideration possible performance issues connected to a large number of server requests, and pages that have to be loaded.

When to use a multi-page application?

An MPA will be best for companies with a large offering of services and products. Those include online stores, marketplaces, and company websites. A multi-page app will be easier to manage and optimize for search engines.

SPA or MPA – what should I build?

Before you start building your app, you should consider its main goals. If you know your service will require multiple categories like, for example, an eCommerce website, you should definitely go the multi-page way. But if you need an easy and simple website, definitely go for a single-page app. A SPA will also be suitable for:

• startups that look for a dynamic platform – as already mentioned, SPAs are a great idea for SaaS platforms, social networks, and closed communities,
• companies that focus on client-side functionalities – if you wish to grab users’ attention with a friendly interface and pleasant interactions,
• businesses with their own API – if you have a ready-to-use API that can be used to build a SPA around it.

There’s also one more solution for you – a hybrid site. As the name suggests, it’s a mix of both, taking the best of both apps and minimizing the disadvantages. It’s like a single-page app that uses URL anchors, allowing in-build browser navigation.

Summary

Single-page applications are all about delivering a seamless user experience and exceptional speed. They’re known for being the perfect fit for social network platforms, SaaS development, and eCommerce stores as they make an amazing base for a future mobile app. 

A SPA development is a time-saving approach, which unfortunately comes with some SEO limitations, so before you jump into the development think about what requirements you have for your website.