Alternative Text
Visual content, including images and media, needs textual alternatives to cater to individuals who cannot perceive it visually. The content of the alternative text (alt text) varies depending on the nature of the visual content: whether it's actionable, informative, complex, decorative, or media-related. Screen-reading tools utilize this text to vocalize content for individuals who are blind or possess diverse sensory processing or learning capabilities. High-quality alt text precisely conveys the image's content and intent, thereby guaranteeing an inclusive user experience for all.
Additionally, alt text plays a role in website rankings as search engines use it when crawling. By ensuring alt text is well-crafted, it becomes an easy way to enhance the user experience for all visitors.
Descriptive Versus Specific
Bad Alt Text
alt="Lighthouse"
This line of alt text technically follows the "be descriptive" rule, but it's too general. The image does show a lighthouse—more specifically, Bodie Island Lighthouse on North Carolina's Outer Banks. It's important to include specifics like that in alt text. Search engines need them to properly crawl the image, for example, if it's on a web page about North Carolina lighthouses.
Good Alt Text
Better alt text for this image might be:
alt="Bodie Island Lighthouse on North Carolina Outer Banks"
Depending upon the subject of your content, you might also mention the scenic landscape.
Who Benefits
Individuals who are visually impaired, including those who are blind or have low vision, face challenges in perceiving images displayed on a page. To ensure equal access to information for this demographic, images must be accompanied by descriptive text alternatives. These alternatives convey the content or purpose of the image, enabling screen readers and braille displays to effectively communicate this information to users who cannot view the images.
Best Practices for Writing Alternative Text
- Describe the image in its context, and focus on the details the image adds to the text.
- Keep alt text concise. Be specific, but try make the alt text fewer than 150 characters. If you need more than a sentence, for example when an image is includes graphs, formulas, or other important complicated text, move the extra information into the visible text of the page.
- Leave out phrases like "image of" or "picture of" in the description. They are repetitive because screen-reading tools identify images from the HTML source code.
- Avoid repeating information that's already covered in a caption or adjacent heading.
- Don't cram in SEO keywords. Search engines crawl alt text but dislike keyword stuffing.
- Use an empty alt tag (alt="") for decorative images that don't contribute to greater understanding of the content. Using the empty alt tag hides decorate images from screen readers. Note: When uploading a decorative image on Digital Commons, select the "Decorative Image" checkbox. You don't need to add the quote marks ("").