You will be told to niche down and you will be told not to box yourself in, often in the same week. Neither is wrong; they apply at different stages.
Niche down when you have no traction
Below a few thousand followers, the problem is almost always that nobody can tell what you are for. A recommendation system cannot classify you confidently, and a human landing on your profile cannot decide in two seconds whether to follow.
Narrowing solves both. It also makes tagging dramatically easier, because a specific account has specific vocabulary.
Broaden when growth is capped, not stalled
Different symptom entirely: consistent performance, engaged audience, but a ceiling you keep hitting. That usually means you have saturated the niche — most of the people interested in exactly that thing already follow you.
The move then is adjacency, not abandonment. Expand into a neighbouring topic your existing audience plausibly also cares about, one step at a time, watching whether engagement holds.
How to tell which you are
Look at your follower growth rate against your engagement rate. Low both: you are unclear, narrow. High engagement with flat growth: you are capped, broaden carefully. High growth with falling engagement: you broadened too fast.
The tagging consequence
Narrowing means moving your tag ladder downward into more specific vocabulary. Broadening means adding a new pillar with its own tag group while leaving the existing one intact. Do not swap your whole tag set at once — you will lose the classification you built.