If you use a fair amount of organizational taxonomies like tags or categories, you’re likely on a CMS that dynamically generates pages for those taxonomies. If not, skip to the next section. If so, Google this:
site:mydomain.com inurl:tag inurl:category
Scroll through and take a look, go to the last page of results. Are there a lot more than you thought? Do you have a lot of /tag/random-tag-name/page/8 type results showing? When you click through to the pages do they look like pages that a user would care about?
Sidetone: If your tag or category or event or whatever pages use a different URL structure, swap that in, e.g. inurl:section
If you don’t see much junk, great!
But if the pages are thin (low content), you probably use a lot of tags or categories just once or twice. If you use a lot of tags just once or twice, not only are you going to see thin content, but you’ll also see a lot of duplicate content in the sense that your /tag/ pages will often show the same one or two articles.
How to fix?
This is tricky.
If you have a taxonomy you don’t care about, then you can just meta robots “noindex” the entire taxonomy and be done with it.
If you know you need to reorganize, delete some tags, consolidate some similar categories, etc., just keep a record so that you can redirect the old names to the new ones or deleted URLs to the most similar still existing URLs.
Sidenote: don’t forget to wildcard redirect your paginated pages
If you don’t know what to delete or not delete, you can check Google Analytics. We typically go back about three years and see what category or tag type pages get real traffic.
Then you can cut the ones with no traffic and/or cut the ones you think are pulling traffic away from where you think they should be. If you go this route, you should test it.
Cutting dead weight content can be incredibly powerful, or it can have no effect.
If you have 2000 posts, and 1500 get less than 5 sessions from organic search a month, you need a more robust plan than testing cutting pages.