Thin content
Thin content is a page with little of value to a reader: too short, copied, auto-generated or written only to rank.
Thin content is a page that gives a reader little or nothing of value. It might be very short, copied from somewhere else, generated in bulk, or written only to catch a search. Length isn't the test. A short page that answers the question fully isn't thin, and a long page that says nothing is.
It matters because search engines try to keep thin pages out of their results, and a site with lots of them can look weaker as a whole. Google's guide to helpful content describes what it looks for instead.
Common kinds
Shops often have product pages with only the manufacturer's description, the same one on fifty other sites. Blogs have tag pages with one post. Some sites make a page for every town they serve, with the same text and a different name. Others publish large numbers of articles generated with little care, which Google calls scaled content abuse.
For example, Harrow & Pine has 400 product pages, each with one line copied from its supplier's catalogue. Rewriting the top fifty with real sizes, care advice and what customers say about them gives search engines and AI platforms something worth reading.
Thin content in AI answers
An AI platform reads pages to find something it can use in an answer. A thin page gives it nothing to quote: no clear answer, no facts, no reason to cite it over the next page. The pages that get cited tend to open with a direct answer and add something specific, like a price, a measurement or a first-hand test.
So the fix is the same for both: answer the question, add what only you know, and merge or remove pages that can't stand on their own.
In AnswerOrbit
Page checks in Recommendations runs eight checks on one of your pages for a prompt, including whether its opening answers the prompt and whether the prompt appears in a heading. It also runs them on up to five pages the platforms cite for that prompt, so you can see how yours compares. See Recommendations.