WordPress itself doesn’t have any limit on the number of tags you can have on each post. You could potentially assign 1,000 or more tags to a post!
However, we definitely don’t recommend that.
The purpose of tags is to help link related posts together. Think of them as an index section in a book. Each tag is like a keyword in the index.
Tags are helpful for users searching your site. Some plugins that display related posts use tags to help them figure out which posts’ topics are related.
We suggest that you normally stick to a maximum of 10 tags per post.