Alt tag, also known as “alt text” or “alt attribute,” is a specification within an HTML code that provides a textual alternative for images on a web page. It is used within an <img> tag to describe the appearance and function of an image on a site. The primary purposes of alt tags are to improve accessibility for visually impaired users who rely on screen readers to browse the internet and to provide context to search engines about the content of the image.

Here are the key aspects and benefits of using alt tags:

1. Accessibility: Alt tags allow screen readers to interpret what an image depicts, which is crucial for users who cannot see the images directly. This makes web content more accessible and inclusive, adhering to web accessibility standards.
2. SEO (Search Engine Optimization): Search engines index alt text, which helps them understand the content of the image and how it relates to the surrounding text. Properly described images using alt tags can improve the visibility of a website in search engine results, especially in image search results.
3. Fallback Content: If an image fails to load on a webpage due to slow connection speeds or coding errors, the alt text will be displayed in place of the image, ensuring that the user still receives relevant information about what was supposed to be there.
4. Compliance with Legal Standards: Web accessibility standards, such as the Web Content Accessibility Guidelines (WCAG), require alt text for images to ensure that content is accessible to all users, including those with disabilities. Failure to comply with these standards can lead to legal consequences for website owners.

When writing alt text, it’s important to be concise but descriptive, accurately reflecting the content and purpose of the image. For SEO purposes, including relevant keywords in alt text can be beneficial, but it’s crucial to avoid keyword stuffing and ensure the text is primarily focused on providing a clear and useful description for both users and search engines.

In HTML, the alt attribute is used as follows in an image tag:

Using alt tags is a best practice in web development and SEO, enhancing both the user experience and a website’s performance in search engine rankings.