What Is Usability?

What is usability?

The term "usability" describes how fit for use a human-computer interface is. In German, usability is often translated as "user-friendliness". Strictly speaking, though, terms like user-friendliness aren't technically correct. Still, that translation has become common in practice and is perfectly fine. The term usability is defined in an ISO standard. According to ISO 9241-11, usability is "the extent to which a product, system, or service can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use. In short: usability makes sure digital applications are easy to use, and it's measured by how directly and quickly users can reach their goal while using the application.

DIN EN ISO 9241

Now that we know what usability is, we've got the most important part behind us, right? Unfortunately not. Because good usability is rarely, if ever, noticed – but bad usability is. An application offers a high level of usability when it meets the requirements of the guidelines for designing user interfaces set out in DIN EN ISO 9241. According to DIN EN ISO 9241, an application should be:

• suitable for the task,
• self-descriptive,
• controllable,
• conforming with user expectations,
• error-tolerant,
• suitable for individualization, and
• suitable for learning

These 7 requirements are also considered the pillars of usability At this point, you have a rough idea of what usability is. But now we're getting down to the nitty-gritty. We'll take a closer look at these 7 pillars of usability. But heads up: this article is 1,886 words long (in the original German version). If you don't have enough time to read it right now, I recommend bookmarking it so you can finish reading it later. The goal of this article is to shed light on all the facets of the term usability.

Suitability for the task:

A dialogue is suitable for the task when it supports users in completing their task effectively and efficiently. This definition includes the 3 criteria for ensuring suitability for the task:

1. Define the task To do this, you first need to identify the tasks that visitors to a website want to or are supposed to carry out. These tasks should be written down and revisited again and again during development so you can check how well the goals are being met.
2. Effectiveness To ensure effectiveness, you have to define when a task counts as successfully completed.
3. Ensure efficiency Ensuring efficiency is the next logical step: you need to define the optimal path. Concretely, this means users must be able to reach their goal with as little time, patience, memory load, and mental effort as possible.

Self-descriptiveness

A dialogue is self-descriptive when each individual dialogue step is immediately understandable through feedback from the dialogue system, or is explained to users on request." At any point, users must be able to answer the following three questions:

1. Where did I come from?
2. Where am I?
3. Where can I go from here?

To make it possible to answer these questions, users need support in the following areas:

Orientation On every page and at every step of a task, visitors need to be given points of orientation so they can immediately tell where they are in the site hierarchy or how far they still are from their goal. Websites often use so-called "breadcrumbs", for example: Website -> Shop -> Category -> Product A -> Reviews

Predictability A page only becomes controllable and manageable for visitors once they can navigate it confidently. The prerequisite for this, however, is that visitors can tell from the design of the navigation elements where they'll take them.

Feedback Feedback on whether actions were successful gives visitors a sense of security, which is essential for building trust.

Help More complex tasks are often hard to carry out, especially for inexperienced visitors. They should be supported in completing their tasks with dedicated help or system documentation

Conformity with user expectations:

A dialogue conforms with user expectations when it's consistent and matches the characteristics of the user, e.g., their knowledge of the work domain, their education and experience, and generally accepted conventions. It's important to distinguish who the target audience is. An application for safety calculations for mechatronics technicians doesn't need to be understood by a hairdresser. On the other hand, a mechatronics technician doesn't need to understand an online shop where hairdressers buy their tools. Humans are creatures of habit. Our actions are shaped by behavioral patterns we've learned over the course of our lives. In the same way, visitors' behavior on websites is shaped by various cognitive, behavioral, and learning-psychology factors:

Consistency The human brain grasps relationships faster when it can recognize familiar patterns. If many important cues – for recognizing navigation options, for example – vary from page to page, users can't store a pattern that would make navigating the next page easier. So on every page, they're busy recognizing and memorizing patterns all over again.

Experience Studies have shown that inexperienced users, in many respects, have no preferences regarding navigation, wording, and workflows. But the more experience visitors gain with different websites, the higher their expectations become that new websites they visit will conform to what they expect. Take the so-called "hamburger menu" (the three stacked lines) as an example: the icon is anything but intuitive. Users who have never seen it don't know what happens when they click on it. Only through experience do they learn the icon and recognize it in different scenarios.

Error tolerance

"A dialogue is error-tolerant if, despite evident errors in input, the intended result can be achieved with either no or minimal corrective action by the user." Potential errors can be classified as follows

Avoidable errors So-called "avoidable errors" mostly occur because not enough attention was paid to user behavior, and could have been avoided with careful target audience research. Typical avoidable user errors in applications or on websites include navigation errors caused by missing orientation cues, or incorrect form entries caused by ambiguous wording. Many software errors caused by programming bugs that produce incomprehensible error messages are avoidable, too. Thorough testing before an application launches could prevent most of these errors.

Known, unavoidable errors Unfortunately, not every known error can be avoided. Accidentally submitting a form that isn't completely filled out yet, or making a typo on the keyboard, are just 2 of countless examples of errors you have to expect. For this kind of error, there's usually a simple, clearly recognizable way to correct it. With forms in particular, data validation can catch many errors and give users the chance to provide complete/correct information.

Unanticipated errors Unanticipated errors happen because of unexpected visitor behavior, or in edge cases that trigger programming bugs that are hard to identify in advance. Most of the time, these errors lead to browser debug messages that users can't understand. Example of web codes: 404 – Page Not Found is usually caught, but status code 500 Internal Server Error isn't. Users don't understand why the system isn't working and leave the application/website. These errors are so bad precisely because users lose trust in the application – and with it, in the company.

Error prevention Careful planning of the site structure and intuitive navigation, along with data validation, can prevent a great many errors right from the start.

Error correction For errors that are known but can't be ruled out completely, you should create clear, easy-to-understand ways to help users fix the error on their own. As mentioned earlier, most "404 Page Not Found" errors are caught. A page then loads that explains to users that the link was wrong and offers them a search function. That way, users can keep working on their task without having to leave the site.

Controllability

A dialogue is controllable when users are able to start the dialogue flow and influence its direction and pace until the goal is reached. For users, applications and websites are fundamentally unfamiliar territory. On unfamiliar ground, users behave uncertainly, in an uncoordinated way, and without a clear goal. The more options they're shown, the more coordinated and purposeful they'll act. If the dialogue is also controllable for users, they lose their fear of making mistakes and handle the application in a more relaxed way than they otherwise would. There are many ways to give visitors a sense of control and the means to exercise it:

• Options to use or turn off media. Autoplay videos have NO business being on websites!
• Alternative navigation options in the text, in a sidebar, or via swipe gestures.
• Making sure the back button or the browser's back function works correctly.
• The home page is reachable at all times
• Ways to cancel at various points

Users' freedom of action is inevitably limited, because the developer decides how many features and navigation options get implemented. Their job, however, is to give users the greatest possible sense of freedom and self-determination in the application. You achieve that when the options on offer match the target audience's expectations so well that there's no need for any more room to maneuver.

Suitability for individualization

A dialogue is suitable for individualization when the dialogue system allows adjustments to the requirements of the task, the user's individual preferences, and user capabilities. Not every application has to let users make individual settings. Still, every application should be designed so that at least the customization options provided by the browser/operating system work flawlessly. For example, zoom, changing the font size, swapping or turning off stylesheets, or disabling multimedia elements without completely losing the context of the content. The more a user is required to engage in dialogue, though, the more customization options they need to be offered. In forums, communities, e-commerce accounts, and other systems built around regular and frequent dialogue, offering personal settings is mandatory and indispensable.

Suitability for learning

A dialogue is suitable for learning when it supports and guides users in learning how to use the dialogue system. How much you need to do to support learning depends directly on how far a dialogue deviates from the cognitive patterns users have stored. These patterns are based on experience with other applications and websites and allow users to apply their knowledge to new websites. Put simply: if users can draw on their experience with other websites and applications to use your application, you've done everything right. Of course, there aren't proven pattern solutions for every type of content and every use case. And of course it's not desirable for all systems to be designed the same way just so they fit stored cognitive patterns. There is, however, a basic rule about how much cognitive load is reasonable: "The less often someone visits a website, the less you can expect them to first have to learn how to use it." However complex the dialogue you need to map may be, your target audience always has a wealth of mental models that let them operate a system built on these patterns with little mental effort. Only in the rarest cases is the path to typical application goals so complex that you have to expect users to learn a new kind of navigation or a new way of completing certain tasks. For inexperienced visitors, though, there are various kinds of support, such as:

• logical page structure
• logical flows
• help pages
• FAQ
• Guided tour
• Visual guiding

But don't forget that this support has to be usable too – otherwise you'll end up needing help for the help 😉

Conclusion

I'll skip a long conclusion. The article is long enough as it is. Together, all 7 pillars add up to a high degree of fitness for use – aka usability. Every designer and every web developer should keep these fundamentals in mind when developing systems. Besides usability, there's also the term user experience (UX) and UX design.