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Hi! That's such a good question, we made an entire resource page about it. (https://moz.com/learn/seo/domain-authority) There's also a video! Domain Authority is a purely Moz metric and is different from Domain Rating. Here's a preview of the video: Domain Authority is a score (on a 100-point scale) developed by Moz that predicts how well a website will rank on search engines. Use Domain Authority when comparing one site to another or tracking the “strength” of your website over time. We calculate this metric by combining all of our other link metrics—linking root domains, number of total links, etc.—into a single score. Feel free to reach out to help@moz.com if you have any specific quesitons,