Alt tags are used as an alternative for images - they are descriptions of the image which can be read by screen readers on the web or by the VoiceOver function in iBooks.
This is an accessibility feature that we recommend that you add to all images in your book.
To add an Alt tag to your image, tap on an image to get the blue border around it, then press the Inspector in the toolbar.
You'll see a field called Accessibility, which is where you enter a description of the image. Try and use a description that would make sense if you were describing the image to someone who couldn't see it.
The image above shows the process of adding an Alt tag to an image and then turning on VoiceOver in the iPad settings so the Alt tag will be read in iBooks.
Go to Settings > General > Accessibility > VoiceOver to activate VoiceOver on your iPad.
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