Perceivable, Operable, Understandable and Robust

Diversity is our world’s greatest asset and inclusion is our greatest challenge.

— Jutta Treviranus,
Director of the Inclusive Design Research Centre
Happy Asian women co-working in an office. One is using a braille display device.

If you visit a website and it loads quickly and looks great to you on your device, you may think that that must mean the site is “Accessible” (because you just accessed it). Some people think “Accessible” means being able to click through to the site successfully from a search result.

Neither of those definitions are entirely correct.

When we discuss website accessibility, what we’re really talking about is the act of creating websites that work, not just for one person on one device, but for as many types of people, with varying abilities, in as many situations as possible.

In order for that to be the case, the site should definitely load quickly, look great on your device and be discoverable in a search. But it’s also important that it works on many, many other types of devices, browsers and screen readers and that it loads quickly, even with slow internet load times.

There are a lot of separate factors involved in achieving this. That’s why the Web Content Accessibility Guidelines (WCAG), that govern such things, group these factors into 4 guiding principles.

The principles seem really obvious when you understand what they mean, but even so, over 80% of websites fail basic accessibility audits.


People should be able to read or hear or watch or otherwise access the information that you provide on your website.

If the text on your website is illegible or invisible or blocked, why does it exist in the first place? You’ve likely put a lot of time or money or effort into creating that content and into making it look fantastic, you must want people to see or access it.

According to the guidelines:

“…users must be able to perceive the information being presented (it can’t be invisible to all of their senses)”.



All of the forms, buttons and interactive elements should work, as expected.

This seems really obvious, but I bet you’ve been to sites where this isn’t the case. Have you ever had a form not work or a pop-up window not close or have you seen links at the bottom of website that you can’t scroll down to?

According to the guidelines:

“…users must be able to operate the interface (the interface cannot require interaction that a user cannot perform).”


Visitors should be able to understand your website and how it works.

This is partly a matter of having clear explanations, but it also helps to have a clean interface and maintain common conventions. For example, most people who have explored the internet understand that underlined text is a link, and is clickable or pressable. If you have a link on your website that isn’t underlined, visitors may not know to click on that text.

According to the guidelines:

“…users must be able to understand the information as well as the operation of the user interface (the content or operation cannot be beyond their understanding).”


Your website should continuously work on most devices.

Different web browsers and screen readers have different capabilities and interpret code differently. Also, the functionality of devices change over time. It’s important to make sure that your website follows standard practices, is responsive to different screen sizes and is kept up-to-date, so it always works.

According to the guidelines:

“…users must be able to access the content as technologies advance (as technologies and user agents evolve, the content should remain accessible).”

Be a people pleaser

It’s tempting to say that these principles have been created to make the web more inclusive to visitors with disabilities. And that would be true. But it also makes the web more enjoyable to navigate for abled users. No one enjoys visiting a broken web page with dozens of flashy ads.

Also, people are amazingly diverse. Everyone has a different combination of abilities, and capabilities change over time. For example, although some people have good vision now, that may change as they age. Imagine gradually being less and less able to do your banking or read the news or contact your family.

I hope we can agree that it’s obvious that these principles are desirable traits for a website to have. Even so, there are thousands of different types of devices, multiple different screen readers, dozens of web browsers and several different operating systems. The combinations of all are endless.

Think of these WCAG principles as goals to continually work towards, but also understand that they are not necessarily easily or perfectly achievable.

There is a current movement that recommends that you under-engineer (or “Tread Lightly” [←see what I did there]) when creating your website. That way you aren’t creating obstacles that you need to work around in order to abide by the principles.

In general, following these principles will make your website a pleasure to visit for almost everyone, which can lead to an increase in visitors that actually stay and explore around.

Let’s POUR the love into your website!

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