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I just did a check and you're right, even though these pages are showing up as errors to the user they are actually showing up as 200 OK, which is causing the duplicate content issue.

Thank you!

We run on Drupal so I'm not sure if there is a 404 plug in

Hi,

I recently noticed an increase in duplicate content, but all of the pages are 404 error pages.

For instance, Moz site crawl says this page: https://www.allconnect.com/sc-internet/internet.html has 43 duplicates and all the duplicates are also 404 pages (https://www.allconnect.com/Coxstatic.html for instance is a duplicate of this page).

Looking for insight on how to fix this issue, do I add an rel=canonical tag to these 60 error pages that points to the original error page?

Thanks!

I just did a check and you're right, even though these pages are showing up as errors to the user they are actually showing up as 200 OK, which is causing the duplicate content issue.

Thank you!