Open almost any TikTok caption and you will find #fyp. It is possibly the most-typed string in social media history, and it does nothing at all.
Information requires difference
A classification signal works by distinguishing one thing from another. A tag that appears on hundreds of millions of videos across every conceivable topic distinguishes nothing. Whatever the system knows about a video carrying #fyp, it knew before it read the tag.
This is not a policy decision or a penalty. It is arithmetic. A label applied universally carries no information by definition.
What the slot could be doing
TikTok captions are short and tags eat characters. Every slot spent on #fyp is a slot not spent on something that describes the video. On a platform where a growing share of usage is explicit search, descriptive tags have real value — a tag naming the specific technique, problem or subject can match a query somebody actually typed.
Is it harmful?
Not directly. There is no evidence of a penalty for using it. The cost is opportunity cost, plus a small perception cost — experienced viewers read it as a beginner tell.
The same logic applies elsewhere
#viral, #explorepage, #foryou and #trending are the same category of tag on other platforms. They describe an outcome the poster wants rather than the content that exists. No classification system can act on an aspiration.
Replace all of them with tags that answer the question "what is this video actually about," and the slot starts earning something.