img and area element
types.Alternative text is especially useful in the following situations:
- For people with low bandwidth connections, who may opt not to load graphics
- For people using handheld devices
- For people with disabilities who use assistive technology, such as refreshable Braille displays or screen readers
- Search Engine Optimization: most search engines interpret the meaning of objects by analyzing their alt attribute
In the early years of Internet development, alternative text was particularly helpful to people using text-only browsers (like Lynx). Nowadays, even when graphical capabilities are taken for granted, alternative text is still highly appreciated by users with accessibility requirements and users looking for ways to optimize their network bandwidth use.
While the use of meaningful alt text is necessary to
comply with accessibility standards, and is good practice,
sometimes an image is used for purely decorative purposes. In
this case, one should use an empty alt attribute (alt="").
The alt attribute is commonly, but incorrectly,
referred to as an image's "alt tag". It is not intended to
provide "pop up" text or tool tips when a user's mouse hovers
over the image, though alt text has historically been presented
in this way in some web browsers; HTML's title
attribute is intended for supplementary information that can be
used in this way. (To use alt correctly and
suppress the tool tip that some web browsers generate, a web
author can use an empty title attribute.)
Example of usage in XHTML
<img src="button_headline.png" alt="Welcome to our website!"/>