The alt
attribute is mandatory
Note that according to the H30 technique of the WCAG
When an image is the only content of a link, the text alternative for the image describes the unique function of the link.
You can use aria-label
to give specific alternative intended to be used by assistive technologies.
For instance:
<a href="http://theblablasite.com/" target="_blank"
aria-label="Visit The Blabla Site Dot Com (opens in a new window)">
<img src="logo_or_whatever.png" alt="The Blabla site" /></a>
The title
attribute can be used to give a tooltip for mouse users if you have visual information to give.
<a href="http://theblablasite.com/" target="_blank"
title="opens in a new window"
aria-label="Visit The Blabla Site Dot Com (opens in a new window)">
<img src="logo_or_whatever.png" alt="The Blabla site" />
<i class="arrow"></i>
</a>
Note, that as this information is not accessible by keyboard only users not using any assistive technology, it can only be used if this comes in complement to any other visual cue (in this example, the title attribute
can be used to explicit the meaning of a small arrow).