Harms of hidden categories on SEO

[CostumeD]

On our website we have some invisible/hidden categories on our site. Can anyone advise whether these are harmful in terms of SEO?

[CleverPhD]

Invisible to who?  If they are invisible to the search engines (e.g. blocked via robots.txt) they could not be harmful, but if you gain any link or other quality equity through those pages, your will not get any additional domain authority or organic traffic to them.

That said, if the hidden categories were resorts of the main categories on your site then you would want to hide them from the search engine as they would be seen as low quality duplicate content.  Otherwise if they were visible they could negatively impact your site.

[Andrew_Birkitt]

Firstly I cannot actually think of any legitimate reason for hiding or making a category invisible, however if you had one that means you don’t want the content to be indexed then you would be best blocking that Category within your robots.txt file.

If it is for any other reason and the content is indexable by ANY search engine not just Google then you run the risk of being penalised.

In fact, Google’s guidelines state that, “hiding text or links in your content to manipulate Google’s search rankings can be seen as deceptive and is a violation of Google’s Webmaster Guidelines

[MickEdwards]

You could legitimately have hidden content in terms of category/URLs - maybe only made available if you sign up as an example.  The guidelines are referring to manipulating on page content so there are elements within that page that are hidden and by default manipulating.