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Hi Corey Don pretty much nailed this answer. I'll make sure to answer your specific questions: You're not negatively affecting your ability to show in search by noindexing tags. They almost never rank or get traffic since they are just pages of thin content. Noindexing them does not affect your other pages. No other repercussions - unless you have a random tag archive getting traffic. Check your analytics, and if so, you can individually leave specific tags indexed with the Yoast plugin. I wrote a post all about this a while back: http://www.evolvingseo.com/2012/08/10/clean-sweep-yo-tag-archives-now/ You would have to figure out how to have unique title tags on each page - which is honestly more effort than is worth it. The Moz tool is showing an 'error' of duplicate content but the issue is just more that tag pages don't have much value and can just be noindexed and then ignored.