What does this mean, actually?
I think that the word definition is offering a good explanation here: “perceivable – capable of being apprehended or understood“.
To apply it to our IT environment – it means that the webpage or application should be understood by ideally all users, no matter what kind of device they are using, and even more important – no matter what kind of potential difficulties their bodies have.
So – perceivable is the key to get our messages out to the user’s mind, so to say. So that user gets it.
Users should be able to understand it in some way, using at least one, or more, of their senses. Seeing it, hearing it, getting the information from braille monitor etc. Ideally in a way we prefer. With all possible controls we would like.
Therefore is not so wise to use a picture as a single source of information. What happens if the picture is not being loaded, for example? Let’s say you are i a tunnel, browsing for information you want and you get a really good hunch when your favorite search engine shows you the results for your query. You click on it, the page opens.
But there is a problem, the tunnel is very long, your internet connection disappears just when the page started to show the picture. And the picture is key to your information.
You are therefore unable to perceive the information for the moment.
The connection is back, you have to reload the page and you can now see the picture. But what if there is a text in the picture that is barely visible in ideal conditions – and you need to read it. Then suddenly the sun shines on your display – you only get the borders of the image and the title of the page – everything else is being blurry due to strong sun reflections.
Again – you will have a problem with understanding. Some things are under your control, you could always move a bit, to see it better… If you can. If it is possible for you. If you are blind and the picture is the only way to get the information, then you can really not do much. The author must try to describe the picture for you. You could try with running the computer vision solution to “translate” the information in the image to you. But it will potentially not be absolutely the same as the author intended it to be.
So – in this example – it is critical that the author thinks about it and if the information is just a picture, then the author should describe it with words and make the text a part of the picture. Ideally visually – showing text and picture is augmenting the sighted users and search engines as well.
That is what perceivable really is about – for users to be able to understand the message you will like them to understand.
