Edit: now I see someone suggest almost the exact same thing already in forum #249598. Oops.

Requested feature overview description.
So then, any page with thumbnails to an on-site picture has JSON strings containing the basic information of each thumbnail, including all its tags in alphabetical order. The information is displayed as a tooltip for its respective thumbnail.

Why would it be useful?
Breaking these tags down by category, preferably in the same order categories are shown on the sidebar (artist, character, copyright, species, general) would make the tooltip easier to interpret (who hasn't wasted time looking at the list of tags trying to find the artist, for example), as well as provide new functionality for client-side userscripts. Not to mention that, apparently, the tooltip text can be changed via stylesheet, so the tags of each category could have the same color as they do on the sidebar.

What part(s) of the site page(s) are affected?
The tooltips of any thumbnail, plus the JSON string responsible for it in the page source. I figure implementing this feature should require relatively little work.

This information is not stored along with the list of tags, it would mean pulling in the tags for every post visible and then splitting on category. This can be prohibitively expensive for where they are displayed and how many can be on each page.

Also, so there isn't any confusion, because this an internal page function it has no stability guarantee, please don't rely on what information is provided to the on page JS because it can and will change without notice based on the needs of the site interface.