Alt Text

Depending on where it appears, the alt text of the BBC's logo might be "Corporate logo of the British Broadcasting Corporation", "BBC" or a null value. In this case, it's the full text of this caption.

File:Alt text.png

Screenshot of preceding images' alt text rendered in lieu of images.

Alt text is an attribute of the HTML's <img> (image) and some other tags.

It is intended to be presented when the image (or other object) to which it pertains is not available to the user, for instance in a text-only browser or a refreshable Braille display. It is also available for indexing by search engines. It is not intended to provide "pop up" text or tooltips 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 the correct attribute to use if this is what is desired.

The presence of the attribute, which may be null (alt="") is a requirement for HTML standard compliance. However (except for purely decorative images, when it should be null), the use of meaningful alt text is necessary to comply with accessibility standards; and is good practice.

Note: Alt text is commonly, but incorrectly, refered to as an image's "alt tag".

External links

• W3C spec section on 'How to specify alternate text'
• Alt text guidance from Alan Flavell with section on humourous gaffes
• Dive in to accessibility page on alt text
• Content Accessibility Tutorial
• Alt text guidelines from Jukka "Yucca" Korpela