Though with modern browsers many are no longer doing the hover over feature for alt-text. This is true of the new versions of Chrome. See - for one source-
https://www.computerhope.com/issues/ch001076.htm
Over all the alt-text is there and is available to be read by screen-readers so ADA compliance is still adhered to, but the hover over is no longer a thing that browser do.
Content Accessibility needs to be considered for access by all students regardless of their learning needs. To ensure that all students are able to access the information they need to be successful, UML LibGuides should strive to achieve these best practices.
LibGuide Structure Best Practices