1.14 Use client-side image maps rather than server-side image maps where possible
WAI checkpoint 9.1
Full WAI text: "Provide client-side image maps instead of server-side image maps except where the regions cannot be defined with an available geometric shape."
Image maps are images which are made up of many parts, each of which is a separate graphical button or link. The different parts are called 'active regions'.
With server-side image maps, the user clicks on a point on the image map and the coordinates of the point they click on are sent to an image map processing application on the server where the site is hosted. With client-side image maps the processing is done in the user's browser.
Client side image maps must be used, unless there is an absolute need to define the active regions with irregular shapes (as opposed to simple geometric shapes like squares or rectangles).
Server-side image maps do not provide adequate support for alt text as it can't be provided for each active region. Alt text is only applied to the map as a whole, which means that they can't be used on non-graphic web browsers or if images are disabled on a graphic browser, thereby preventing users from accessing any of the links.
Also, server-side image maps rely on -point and click' interaction with a mouse, making them unusable by keyboard only navigation, i.e. for users of laptops without a mouse, screen readers, touch screens or special pointing devices.
However, client side image maps are not suitable for some applications. For example, a co-ordinate based geographical information system would be very difficult to present by building a client side image map from thousands of individual images, each with it's own alt text.
Directions and Techniques
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How you could check for this:
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