Tips & Tricks Thursday 01: Alt Text, Caption, Description

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Alt Text, Caption, Description… Which was What Again?

The terms Alt Text, Caption, and Description are often used in the context of images, especially regarding accessibility, but they serve distinct purposes. Here’s a breakdown of their differences, recommended content, and examples for each.

Alt Text (Alternative Text)

Purpose: Alt text is used to describe the content and function of an image for people using screen readers or if the image fails to load. Its primary role is to provide context to users who can’t see the image, enabling them to understand what the image conveys or why it’s included.

Content: Alt text should be concise, but informative. It should focus on the image’s essential meaning in the context of the page and convey any important information or action associated with the image.

Best Practices
• Keep it short (ideally under 125 characters).
• Avoid phrases like “image of” or “picture of.”
• Only describe the image in as much detail as is necessary for comprehension.

Example #1
• Image: A button showing a shopping cart icon.
• Alt Text: “Add to cart.”

Example #2
• Image: A graph showing a steady increase in sales over the past five years.
• Alt Text: “Sales growth from 2019 to 2024.”

Caption

Purpose: A caption is visible text that provides contextual information about the image. It often supplements the image by offering additional details that may not be obvious from just looking at it. Unlike alt text, captions are intended for all users, not just those using assistive technology.

Content: Captions can be a bit more detailed than alt text. They often describe what’s happening in the image, offer context for how the image relates to the surrounding text, or even include a brief commentary or title.

Best Practices
• Be informative, but concise.
• Ensure that the caption supports the surrounding content.
• Avoid redundancy with the alt text.

Example #1
• Image: A photo of a team in a meeting room.
• Alt Text: “The design team discusses the upcoming product launch during the Monday meeting.”

Example #2
• Image: A historic photo of the first man on the moon.
• Alt Text: “Neil Armstrong takes the first steps on the moon, July 20, 1969.”

Description

Purpose: An image description provides a longer, more detailed explanation of the image. It’s especially useful for complex images like graphs, charts, or illustrations that require in-depth understanding or contain important data. Descriptions are often part of the main text or can be provided in a separate figure description section.

Content: The description can offer full context and detail about the image, explaining elements that require more than a brief mention, such as relationships in data, intricacies in an image, or additional background information.

Best Practices
• Provide thorough explanations for images that require it.
• Avoid redundant information that’s already conveyed by the alt text or caption.
• Ensure the description fits the needs of the content and audience.

Example #1
• Image: A detailed bar chart showing revenue growth by region.
• Alt Text: “The bar chart shows revenue growth across four regions: North America, Europe, Asia, and Latin America, from 2019 to 2024. North America saw the highest growth, increasing by 30% over the period, while Latin America had the smallest growth, with a 10% increase. This illustrates the significant disparity between market performance in different regions.”

Example #2
• Image: A complex flowchart illustrating the process of user onboarding in a software application.
• Alt Text: “The flowchart outlines the user onboarding process, starting with registration, followed by email verification, profile setup, and ending with a welcome tutorial. Each stage includes a decision point where users can either proceed to the next step or return to a previous one if they encounter an error or need more information.”

Quick Summary of When to Use Each

By combining all three – alt text for screen reader users, captions for general context, and detailed descriptions for complex content – you create an inclusive and well-rounded experience for all users.

Alt Text: Used for screen readers or when an image doesn’t load; essential for understanding the image in brief.
Example: “Graph showing increase in sales.”

Caption: Visible to all users, placed near the image to give context or additional details.
Example: “Sales have grown steadily for the past five years.”

Description: A more detailed explanation of the image, often necessary for complex visuals or images with intricate meaning.
Example: “The graph illustrates quarterly sales figures from 2019 to 2024, with an overall increase of 25%.”

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