Single-page applications (SPAs) — what they are and how they work

With interaction and personalization becoming increasingly important in web development, single-page applications (SPAs) have emerged as one of the most popular ways for creators to display content while engaging with users. This approach can optimize page performance and user experiences, but it might not always be the best choice when deciding how to build your project. After all, multi-page applications (MPAs) have their advantages too.

When choosing how to create your content, it’s beneficial to know the benefits and challenges of using SPAs and understand their use cases compared to how MPAs work.

In this article, we’ll take a closer look at how single-page applications function and how teams can decide on the best tools and frameworks to support their development. To do this, we’ll discuss:

• What is a single-page application?
• Single-page applications vs. multi-page applications — key differences
• Pros and cons of single-page applications
• The best frameworks for your SPA
• Examples of single-page applications

What is a single-page application?

A single-page application is a website that loads a single document and overwrites the existing page with new data from a web server rather than reloading pages individually from scratch. As a result, page content updates in real time based on user actions with quick transitions and without refreshing.

The ability to provide new content seamlessly based on user actions, such as button clicks or field-level submissions, is what makes single-page applications stand out from their counterparts. Instead of refreshing an entire page of content, the application updates or alters components based on the user’s action and needs, making it quick to respond and easy to interact with in real time.

Users also can connect with updated information without waiting for pages to load. In areas like ecommerce where time spent is money, the continuous experience can have a deep impact on the bottom line. The likelihood that someone will leave a page (called a bounce) jumps 32% when load times increase from just one to three seconds.

While the user is exposed to a single webpage, SPA architecture involves both client-side and server-side rendering components. When a user initially visits a single-page application, the browser is sent an HTML file with corresponding assets. From there, an application programming interface (API) is used to send user information and new content back and forth to the SPA in real time. The structure also allows for separate back-end and front-end development with reusable code.

Single-page applications vs. multi-page applications — key differences

While single-page applications have risen in popularity due to their real-time interaction with users, there are other ways to achieve this result. Multi-page applications are the traditional alternative to SPAs. The key difference is that MPAs require a new page load every time information is updated. While this can add more complexity, it can also provide developers a means for handling large amounts of data across an ever-changing user interface.

Multi-page applications have a varied architecture from their SPA counterparts. Each time a user takes an action (for example, clicking a link or submitting form information), the website must send new data for an HTML page reload, along with changes that reflect the user’s actions.

This can result in longer build times for developers and longer load times — because the front end and back end must communicate with one another to make frequent updates to what the user sees on screen. Developers should be aware that repeated page content loading can impact the user experience.

While this can be unwieldy in some instances, MPAs have their place with websites that have a lot of content to serve to visitors. They have remained a staple of web development for sites such as blogs and vast ecommerce sites that feature catalogs of products and services.

Pros and cons of single-page applications

Remember, the biggest difference between MPAs and SPAs is that a SPA will render new information on the same HTML page rather than reloading to display new content each time. This results in the most critical of benefits when comparing the two application types — faster load time.

SPAs are known for being quick to load and easy to keep visitors engaged with their current process, whether requesting more product information or entering their payment details. This makes users less likely to bounce, or leave a page prematurely, such as before a transaction has been finalized.

Of course, the differences and benefits of single-page applications do not stop there. Here are some of the most important differentiators for developers and teams to consider when evaluating SPAs.

Benefits of single-page applications

The most important benefits of single-page applications include the following:

• Improved speed and responsiveness. Faster loading times are the result of the SPA only needing to load the information necessary based on the user’s action rather than loading an entire page from scratch.
• Greater stability. This includes caching capabilities and reduced bandwidth usage, which allow the pages to be displayed even where internet connections might be faulty.
• Better UX. Since pages load quicker and appear interactive, users are more engaged and have an improved experience working with the content presented.
• Faster development. SPAs can take advantage of a number of different APIs, allowing developers to work separately on the front end, back end, and connections that drive content more iteratively.
• Easier debugging. This flexibility also applies to testing and fixes since codebases tend to be more modular and allow developers to work on different parts at the same time.
• Cross-platform compatibility. Since SPAs can use a single codebase, they can also be designed to run on any platform or browser, giving users a seamless experience as they switch devices.
• Mobile-friendliness. Code can also be reused to design mobile apps and responsive pages that display just as well on phone-based browsers and apps as they do on desktop devices, supporting mobile users without loss of functionality.

Challenges of single-page applications

While single-page applications have their advantages, common issues associated with SPAs include:

• Difficulty scaling. Increased traffic or website rendering difficulties could arise since SPAs often remain dependent on a limited number of servers for loading and supporting the user experience.
• Security risks. With most of the heavy lifting done on the client side, SPAs remain susceptible to attacks that can inject malicious code that executes within the browser. These attacks can be prevented by following proper security measures including Content Security Policy (CSP).
• SEO disadvantages. Since only a single page is rendered as part of a SPA’s architecture, they remain difficult to optimize for search engines that reward based on page count and content creation. However, Google has begun to provide better tools for indexing SPAs.
• Site analytics. These will require a hands-on approach since a single page is being rendered, making it harder to determine website traffic or where users drop off in a customer journey.
• Navigation challenges. Content must be designed to fit the existing user experience through each new presentation of information to eliminate awkward scrolling within a page. These concerns also apply to navigation since the back button does not function the same in a SPA.
• JavaScript. For users who have JavaScript disabled, either by choice or by their corporate IT team, SPAs simply will not work. JavaScript is required for rendering the user interface that a SPA relies on, making this problematic in some instances.
• Memory leaks. Some frameworks can cause memory to be allocated when it is no longer needed, which can impact application performance.

The best frameworks for your SPA

With a better understanding of how single-page applications work, as well as their benefits and disadvantages, leaders can begin to choose an approach for their SPA. These frameworks — or structures for building programs and interfaces that interrelate — can be used to maximize the benefits of a single-page application depending on an organization’s unique needs.

Here are just a few of the most popular frameworks used to develop SPAs.

• Angular. One of the top frameworks available, Angular is overseen by Google and includes options for client-side technology. It is highly responsive, with quick loading and easy navigation. Angular is also a great fit for applications that transfer information, such as news, weather, travel, and social media apps.
• React. Created by Facebook, this framework includes a catalog of UI components that can simplify development for real-time applications. It is best used for dashboards, ecommerce stores, and job portals, to name a few examples of dynamic content. ReactJS is also more SEO-friendly than other options and can be read by Google.
• Vue.js. Great for beginners, the VueJS framework is considered easy to use and includes drag-and-drop options for developers to get started with the components they need most. Developers can also use CSS alongside it with relative ease.
• Aurelia. Licensed under MIT, this open-source framework allows for broader integration with other frameworks for more flexible development. A newer entry into the field, Aurelia simplifies configuration setup and supports a number of different languages including TypeScript.
• Backbone.js. A better fit for smaller pages, Backbone does not perform data binding, which can impact performance for larger applications. However, it tends to perform faster when working with smaller data sets when compared to more broadly accepted frameworks like Angular.
• Ember.js. This framework supports flexible projects that involve complex HTML. This open-source option can be used to create enterprise-level applications due to its robust ability to handle back-end architecture.
• Knockout.js. For less complex SPAs, Knockout can be used to define key user interface components with relative ease. While this can be achieved through other frameworks, Knockout provides an advantage for developers looking to define their own application structure, which can afford greater UI flexibility.
• Meteor.js. Another option for less-experienced developers, Meteor includes libraries and packages that make the tool easy to use. It is also supported by a community that offers additional packages to grow out features. Notably, server-side debugging is supported along with powerful testing tools.
• Polymer.js. This choice is best suited for users looking to build customizable and reusable HTML components for SPAs. While more akin to a library than a full-fledged framework, Polymer supports CSS use for creating web components alongside HTML and JavaScript.

Examples of single-page applications

Single-page applications are more prevalent than most leaders may imagine. With the many benefits of leveraging a catalog of frameworks while helping developers create dynamic, real-time content that is quick and easy for users to interact with, SPAs are increasingly taking center stage with some of the world’s major brands and platforms.

Here are just a few clear examples of SPAs:

• Gmail. Users do not need to refresh the inbox page to receive new email messages. The SPA that runs Gmail, along with Google Calendar and Drive, automatically presents new content as it is received from the server.
• Slack. The channel-based messaging platform uses ReactJS for its web version, making it faster for real-time messages to come through via a single webpage.
• Trello. No page reloading is required for collaborators on the Trello platform either, which uses Backbone as part of its configuration. Users see real-time updates as others add projects, change statuses, and work across devices.
• Netflix. Despite the vast amount of content available to users, Netflix is an example of a SPA. Visual signs of this include a consistent page header and navigation throughout, while behind the scenes, the application runs, in part, on React.
• Grammarly. Using Vue, this application provides real-time grammar suggestions within the web browser and often with other applications themselves.

Capitalize on the benefits of single-page applications

Single-page applications can be a great choice for brands looking to enhance their user experiences and create more connections with customers throughout their journeys. The key is to select a framework and approach for your business that is also a fit for the development team you have on hand. The right SPA will not only improve speed and responsiveness of a website, but it will also provide faster development and more flexible debugging solutions to keep things running smoothly for the long term.

Choosing to create a single-page application is just the start. Once a development team has carefully crafted content to meet the demands of the business, leaders will need ways to capitalize on the benefits of their work and maintain it over time.

Adobe Experience Manager can be used to manage and edit single-page applications with a hybrid content management system designed for ease of use. Manage pages created with frameworks like React and Angular while leveraging drag-and-drop elements that make change management seamless. Experience Manager was created to make in-context, real-time editing straightforward for managers and developers alike.

Learn how Experience Manager can supercharge your single-page application with out-of-the-box components that save time and support responsive web design. Watch our quick demo to see Experience Manager in action.