Not to be confused with the meta category of tags on a post's tag list.

This invalid tag appeared on a post because someone tried to use something like a screen resolution, aspect ratio, content rating, etc. as a tag. Having these as separate tags is unnecessary, as the site has a built-in system for freely searching for these in what's called the "metatag" system. A guide that shows these types of searches can be seen at the Search Cheatsheet. Here are some example search queries from that cheatsheet:

• ratio:4:3 - searches for every post with a 4:3 aspect ratio
• width:3840 height:2160 - searches for every post with a resolution of 3840x2160 (4K)
• rating:s or rating:safe - searches for every post that has a safe rating
• order:favcount - sorts every post on e6AI by most favorited to least favorited

If you see this tag on a post, simply remove it.