What is the purpose of alt text in web design?

Alt text, or alternative text, serves a crucial role in web design by providing a descriptive explanation of images. This is particularly important for accessibility, as it allows individuals using screen readers or other assistive technologies to understand the content and function of images on a webpage. For users who are visually impaired or have difficulty seeing images, alt text conveys the same information that a sighted user would get from viewing the image.

By including alt text, web designers ensure that all users, regardless of their abilities, can access and interpret the information presented on the site. It also contributes to better SEO practices, as search engines use this text to understand and index images, improving the website's visibility.

The other responses do not accurately capture the purpose of alt text. For example, enhancing website colors pertains to visual design choices rather than content accessibility. Loading images faster relates to technical optimization and is not influenced by the presence of alt text. Similarly, creating image backups is a different concept altogether, focusing on image storage rather than accessibility or content description. Hence, the emphasis on accessibility through descriptive alt text is the core function it serves in web design.