Here are a tew quick guidelines you can employ to create or improve the quality of a piece of alt text.
Don’t start with Image of…
Unless otherwise stated, it is assumed that alt text is describing a photo. Alt text does not need to include phrases such as This is an image that shows… or This is a photo of… It is sufficient to use wording such as Bar chart shows… or Aerial map showing… Alt text should simply describe the meaningful elements of the photo.
Be brief but meaningful.
Although alt text should be brief, if your graphic displays numbers or a trend or quantitative information, your alt text should as well. A phrase like Bar chart showing sales for 2022 is brief but does not give readers enough detail. Alt text should convey in words the same information that is communicated by the image so readers understand its significance and purpose in the document: Bar chart showing a steady increase in sales from 2011 to 2021 ending with a high of $1.3 million.
Do not include figure numbers and titles as alt text.
The screen reader will read the figure number and title before it announces an image so including that information in the alt text would be redundant. If, however, the number and title are embedded in the figure (such as on a map), then include the number and title in the alt text because the screen reader does not read every word on an image. Continue by adding alt text to describe the meaning of the image.
Avoid alt text descriptions that rely on color. Avoid using color to describe elements in your image or figure such as “Red icons on the map indicate road blocks.” Someone may not be able to see how many or where they are, so describing items in this way provides no useful information. A better description would be “15 red icons show a concentration of roadblocks around 15th Avenue and Main Street.”
Be quantitative when it matters.
Suppose your report includes a photo of a crowded highway and a chart of traffic patterns. Whether 37 or 29 vehicles appear in the photo doesn’t matter; readers need to know the scene is a road clogged with traffic. For the bar charts, numeric details do matter and are vital to understanding. The appropriate alt text could be Bar chart shows traffic significantly increases on Thursdays and Fridays between 5:00 p.m. and 6:00 p.m.
Keep punctuation simple.
When writing alt text, use correct punctuation (so the screen reader knows when to pause). Commas are short pauses, and periods are long pauses. Avoid excessive punctuation within the alt text.
Avoid acronyms, links, and excessive symbols. Alt text should not include URLs, excessive symbols, bulleted entries, or other non-text elements. Each screen reader may interpret these items differently. Some may ignore them, and others are simply not accessible, as in the case of hyperlinks.
rom “Writing Effective Alt Text” in issue 11 of CreativePro Magazine.
This article was last modified on September 9, 2024
This article was first published on September 9, 2024
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