Mind your audience!

One important thing to take into consideration when describing images is your audience.

Target audience vs actual audience

Notice how I didn't write "target audience". This is one of the points at which this wiki differs from other alt-text guides, and at which posting images into the Fediverse differs from adding images to a website or a blog post.

For a website or a blog, you can define the target audience, and then you can make sure with surgical precision that your actual audience won't go beyond your target audience. You can use SEO, you can give the link to your website or your blog only to the right people, and you can be pretty certain that only the people will come whom you want to come.

Your website or your blog can be about an extremely obscure niche topic that next to nobody knows about. But even then you can make sure that only those people who do know about this topic will come. People to whom you don't have to explain anything because they're already familiar with the topic.

You pull visitors to your website or your blog. And you have all control over whom you pull in.

In the Fediverse, this is vastly different. In the Fediverse, you can't pull readers to your content. You push your content to the readers. And you normally barely have any control over who'll receive it.

Sure, you can make sure that only those follow you who really know about the topic that you post about. But if your posts are public, they also appear on the public timelines of all the servers that are home to your contacts. And these timelines are certainly checked by people who know nothing about what you post about.

Also, chances are that one or several of your contacts like one of your obscure niche topic posts so much that they boost/repost/renote/repeat it. And most of their contacts don't know a thing about what you write about.

On a blog or a website, you can write specifically for a well-informed target audience. In the Fediverse, you have to write for just about everybody, regardless of what they know and what they don't know.

Considering your audience

This also means that it's your responsibility to make sure that your actual audience get all the information they need or want.

The first question that you have to ask yourself is:

• Who is my audience? (Answer: potentially everyone in the Fediverse, maybe even everyone on the Web)

Next, you have to ask yourself:

• What do they know about what my image post is about and what my image contains?
• What don't they know about it?
• What can they realistically know about it?
• What do they need to know to understand the image and the post that they don't know?
• What do they need to know about the content of the image that they don't necessarily know?
• What may they want to know about the content of the image in addition to the above that they don't necessarily know? What has the chance of making them so curious about the image that it requires being described?

Also, consider this:

• What is the alt-text and image description culture like in the places where my audience is?

The answer to the latter is that the alt-text and image description culture in the Fediverse, particularly if your post has a chance of ending up on Mastodon, is a whole lot different from the situation on websites and blogs. Certain W3C WAI and WCAG rules don't apply. At the same time, there are rules that do apply that don't exist in the WCAG. For example, you must never omit details and expect Mastodon users to be willing to ask about them. Mastodon users are used to being pampered and coddled. At least some of them expect you to deliver any and all information that they may want to have right away.

For example, if you mention that there is something in the image, and not everyone knows what it looks like anyway, you're required to describe what it looks like. Ask yourself whether it's commonly known what the contents of your image look like. Not in your niche bubble, but among the general public. If it isn't, describe it. If this makes your image description longer than 512 characters, put it into the message text, and then distill an additional shorter description from it and put it into the alt-text.

Also, Mastodon users love to have explanations delivered with image descriptions if they need explanations to understand the image. Now, explanations must never be added to the alt-text because some people don't have any access to alt-texts. So the explanations must always go into the message text. Again, ask yourself whether what you post an image about is commonly known with no need to explain it. Again, not in your niche bubble, but among the general public. And again, if it isn't, explain it. If you already have a long description in the message text (and, of course, a shorter description in the alt-text), you can combine the explanations with the long description.