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Hi there! Tawny from the Help Team here. Thanks for writing in - this is a great question. In order to find the page our crawler was on when it encountered a 404 error, I'd recommend requesting the full crawl CSV via the 'Email CSV' button in your 'Site Crawl' section. From there, you'll want to check the referrer URL for the page that 404s. To do that, find the URL of the page in column A of the CSV and locate the referrer URL for that page in column AM. The URL in column AM is the page our crawler was on when it ran into the link for the page that results in a 404 in the browser. I hope this helps identify where these are coming from - if there's any additional information you're needing, please don't hesitate to let us know! You can write in to help@moz.com any time if you need a bit more guidance.