What is alt text?

Alt text, or alternative text, is a crucial HTML attribute that provides a textual description of images on a webpage. It serves multiple purposes, primarily enhancing web accessibility and improving search engine optimization (SEO).

Definition and Purpose

Technical Definition: Alt text is defined as the text that is associated with an image in an HTML document, typically included within the alt attribute of an <img> tag. For example:

xml<img src="example.jpg" alt="A description of the image">

Functionality: The primary function of alt text is to convey the content and function of an image when it cannot be viewed. This includes scenarios where:

• The image fails to load due to network issues.
• Users have disabled image loading in their browsers to save data.
• Users rely on screen readers because of visual impairments.

In these cases, screen readers read the alt text aloud, allowing visually impaired users to understand the context and content of the images they cannot see.

Importance in Accessibility

Alt text is essential for making web content accessible. According to the Web Content Accessibility Guidelines (WCAG), all non-text content must have a text alternative that serves the same purpose. This ensures that users with disabilities can navigate and comprehend web pages effectively.

Screen Readers: These assistive technologies utilize alt text to describe images, enabling users who are blind or have low vision to engage with visual content. Additionally, well-crafted alt text can aid users with cognitive disabilities by providing clear and concise descriptions of images.

Role in Search Engine Optimization (SEO)

From an SEO perspective, alt text plays a vital role in helping search engines understand the context of images. Since search engines cannot interpret images directly, they rely on alt text to index and rank content appropriately.

Ranking Factors: Alt text contributes to a webpage’s overall SEO by:

• Providing semantic meaning to images.
• Enhancing the likelihood of appearing in image search results.
• Improving page rankings through better contextual relevance.

Best Practices for Writing Alt Text

When creating effective alt text, consider the following guidelines:

1. Be Descriptive and Specific: Clearly describe what the image depicts without being overly verbose. For instance, instead of using generic phrases like “image of,” directly state what is shown (e.g., “A brown bear standing by a stream”).
2. Context Matters: Tailor your description based on the image’s context within the page. If an image is central to understanding a topic, provide more detail; if it’s decorative, a brief description may suffice or even be omitted entirely.
3. Avoid Redundancy: Do not include phrases like “image of” or “picture of” since screen readers already identify it as an image.
4. Limit Length: Aim for brevity; most screen readers truncate alt text at around 125 characters. Ensure you convey essential information succinctly.
5. Use Long Descriptions When Necessary: For complex images that require more context, consider using additional attributes like longdesc or providing a detailed description elsewhere on the page.

By adhering to these practices, you can enhance both accessibility and SEO performance through effective use of alt text.