What is banned hashtags?
Also called restricted hashtags.
Banned hashtags are hashtags a platform hides or limits, usually because they were used for spam or content that breaks its rules, so posts using them get less reach.
Why it matters
A single restricted tag can make a post harder to find, and Instagram doesn't publish a full list, so it's worth checking tags before you use them.
Example
A fitness account notices a post isn't showing up under its hashtags and finds that one of the tags it used is restricted.