The alt attribute is used in HTML and XHTML documents to specify alternative text (alt text) that is to be rendered when the element to which it is applied cannot be rendered. In HTML 4.01, the attribute is required for the
area tags. It is optional for the
input tag and the deprecated
The syntax of the alt attribute is:
Here is an image whose alt attribute is "In the sky flies a red flag with a white cross whose vertical bar is shifted toward the flagpole."
The HTML for this image might be something like the following:
<img alt="In the sky flies a red flag with a white cross whose vertical bar is shifted toward the flagpole." src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Dannebrog.jpg/180px-Dannebrog.jpg" width="180" height="135" />
A visually impaired reader, who is using a screen reader such as JAWS or Orca, will hear the alt text in place of the image. A text browser such as Lynx will display the alt text instead of the image. A graphical browser typically will display only the image, and will display the alt text only if you ask it to show the image's properties. Many graphical browsers can be configured to show the alt text instead of the image.
Internet Explorer 7 and earlier incorrectly renders text in alt attributes as tooltip text. This behavior led many web developers to use alt to display tooltips on webpages, instead of using the
title attribute that was intended for that use. In Internet Explorer 8 the bug was fixed, and alt attributes no longer render as tooltips.
- ↑ Why doesn’t Mozilla display my alt tooltips?. Retrieved on 22 July 2009.
- ↑ 2.0 2.1 Anne van Kesteren (16 December 2004). Alt attribute (alt tag, alt tooltip). Retrieved on 22 July 2009.
- ↑ Bug 25537 - Alt text is not displayed as a tooltip over <img>, Mozilla bugzilla
- ↑ W3C HTML WG (24 December 1999). 7.4.3 The title attribute. HTML 4.01 Specification. W3C. Retrieved on 22 July 2009.
- ↑ What's New in Internet Explorer 8 – Accessibility and ARIA. MSDN. Microsoft. Retrieved on 22 July 2009.
- ↑ Roger Johansson (7 November 2005). It’s alt attribute, not alt tag. 456 Berea Street. Retrieved on 22 July 2009.
- ↑ Tommy Olsson (20 July 2004). Alt tags. The Autistic Cuckoo. Retrieved on 22 July 2009.
- How to specify alternate text from the HTML 4.01 specification
- Providing text equivalents for images from Dive Into Accessibility
- Guidelines on alt texts in
imgelements by Jukka Korpela
- Alternative text for images: the alt attribute by Estelle Weyl
- Mini-FAQ about the alternate text of images by Ian Hickson