The Web Design Group presents:

Summary

ALT text recommendations, and notes on viewing situation.

The ALT text provides alternative or substitute text, for use when the image is not being displayed. The most common mistake (apart from not using it at all) is to provide a description of the image, without considering what job the image was doing on the page, leading to results that can range from the incongruous to the absurd. The ALT text should be composed as an appropriate textual alternative to the image: sometimes that might turn out to be a description of the image, but in practice that seems to be wrong more often than it's right.

The advice here is offered as a good compromise that works in all three types of viewing situation, with notes on the consequences for the different types.

For "Type I: graphics enabled" users: some browsers will display the ALT text while waiting for the IMGs to load - the ALT texts recommended here seem to be at least adequate for that situation, so it's not discussed in any detail.

  ALT recommendation: Type II:
those browsing in text mode, but having image viewing available if required
Type III:
text mode only (e.g character mode terminal, blind readers etc. and indexing robots)
a) Page decorations Code ALT="" in most cases;
for bullets ALT="*" etc.,
(for rules maybe ALT="- - -", ALT=". o O o ." etc. but this is deprecated by accessibility guidelines)
Reader is unlikely to want to view the image. Don't use an ALT text that is a description of the image ("Fancy rule", "Left filler pattern" etc). "ASCII art" decorations can be intrusive on a speaking browser, so use ALT="" if you possibly can.
b) Navigation icons ALT="Next", "Previous" etc. ALT="Foo Corp. Home Page" ("To: Foo Corp. Home Page", if you must, but not "Back to.." or "Return to.."). Think about graphical browsers that chop or suppress the text display if the IMG's HEIGHT/WIDTH is too small. If possible, arrange it so there will be no more than one anchor per displayed line.
c) Supplemental or interesting Sometimes a brief description of the image is appropriate: more often it's better to state what it was that the image was intended to illustrate. You may want to mention the image file size, if it's substantial. The text helps the reader to decide whether they want (or need) to load the image. Don't frustrate the reader by claiming that they must load this image.
d) Essential, critical for understanding the page Be honest with your readers, tell them frankly (e.g in the ALT text) that this image is essential to your presentation. Don't do this unless you have to, though, or readers might go to extra trouble (blind readers enlisting the help of a friend, say) and then be disappointed (see previous entry).

These recommendations essentially pre-date the availability of TITLE and LONGDESC in browsers. Some modest reworking can be expected later, to exploit these enhancements.


To: the article "Use of ALT texts in IMGs"


The contents of this article were originally published at http://ppewww.ph.gla.ac.uk/%7Eflavell/alt/alt-table.html, where they are currently maintained.

Original materials © Copyright 1994 - 1998 A.J.Flavell & Glasgow University


Web Design Group