Non-text content

Non-text content should be supplemented with a text alternative (alt text). This text can be converted by assistive technologies into a format the reader needs, including Braille or speech.

Whenever possible, this text-alternative should serve an equivalent purpose for the end-user. There are cases where this might be difficult, such as an audio-based test, or an audio-visual sensory experience. In these cases, alt text should at least provide descriptive identification of the non-text content.

Non-content

Some non-text elements aren’t really meaningful content at all. If an element is purely decorative, does not convey useful information, or provides visual formatting that does not affect the meaning of the content, it should not have any alt text applied. These non content elements should instead be implemented in such a way that they will be ignored by assistive technology.

Effective alt text doesn’t just provide useful descriptions of non-text content. It also respects the user’s time; further, it is written with clarity, economy and structure.

Functionality

First and foremost, consider the function of the non-text content. What is it meant to communicate to the reader? For instance, if an image of the Bluesky logo is being used as a link to the organization’s Bluesky feed, the alt text could simply read:

Bluesky feed

When using an image as a link, the alt text should specify where the user will be directed.

Relevance

Always consider the audience, context, and intent of non-text content. What relevant information is this content intended to communicate? Sometimes a literal description is warranted, but typically describing the communication intent is more useful. Consider the following text alternative for an image.

Logo for the Association of Registered Graphic Designers, consisting of a red rectangle containing the capital letters RGD in white, set in the sans serif typeface Classic Grotesque.

A description like the above might be useful if the image was appearing in a book about logo design. However in most cases, a logo is used to communicate an entity’s name, and so the following alt-text would be more appropriate.

Association of Registered Graphic Designers

Note that alt text should generally be written in Sentence case, meaning the first word is capitalized, and the rest of the words are lowercase – unless they are acronyms or proper nouns.

Embedded text

If there is text in the image, it needs to be included in the alt text if it provides important information or context for understanding the content. Here is an example:

The front page of the Globe and Mail newspaper from July 21 1969, with the headline “MAN ON MOON.” The text continues: ‘‘‘It’s pretty up here… a fine, soft surface.’ Talking Neil Armstrong into taking a first step.”

There is of course more text on the front page of the newspaper. Use your discretion to discern how much text is required to communicate the necessary message in the image to a non-sighted user.

Length

Effective alt text is written with economy. It is usually one or two sentences long. However, there may be cases where only a couple of words are needed and other cases where more than a couple sentences are necessary. If a shorter description cannot communicate all of the relevant information being conveyed by an image, a longer description is warranted.

Structure

When writing a longer description, start with a concise alt text to help the reader decide if they are interested in the longer description or not. Whenever possible, structure your alt text writing to mention the most important details first. Ideally, details should be arranged in descending importance, so the reader can continue if they want to know more, or skip ahead when they’ve read enough.

Objectivity

Avoid subjective judgements or opinions when writing alt text. There is a fine line between making a useful inference about the intended meaning and providing an assumptive subjective opinion. When you write alt text, try to think of yourself as an objective and neutral journalist, giving the reader what they want to know in order to make up their own mind about the content.

Redundancy

When writing alt text, avoid redundancy. Don’t repeat content that is already present on the page. For instance, if the text from The Globe and Mail newspaper from July 21, 1969, is already included in the content of the page, the alt text could simply read as follows.

Front page of The Globe and Mail Newspaper from July 21, 1969.

Note that even this is redundant. A better approach might be to include no alt text at all, and to instead format the image to remove it from the screen reader’s view.

Unnecessary words

Don’t start your alt text with the words “image of,” “picture of,” “video of,” “link to,” or any other similarly generic description that should be self-evident from the semantic structure. For instance, consider the following alt text for an image.

Image of the Loch Ness Monster emerging from the water in daylight.

The first two words are extraneous and they delay the user from reading the relevant meaning.

Necessary words

In some cases however, describing the media more specifically could give additional important context. Consider the following two examples of alt text.

Drawing of the Loch Ness Monster emerging from the water in daylight.

Photograph of the Loch Ness Monster emerging from the water in daylight.

In these cases, describing the form of the media makes a meaningful difference in how it might be understood.

Finish it

Lastly, always end your text with a period to provide a pause between elements, just as you would with any good writing.