> but the concept of domain authority doesn't exist.

I would argue that it does.

I spent 3-4 years deep in the blackhat SEO world - it was my living, and it almost completely was dependent on free subdomains because they ranked _so much better_ than fresh purchased domains.

Let's use a real world example.

Insert free dynamic dns service here - you create a subdomain on one of their 25-100 domains, provide an IP address for that subdomain and.. whala, spam site.

So let's say we've now got spam-site-100.free-dynamic-dns-service.com - it's a record is pointed to my host, I'm serving up super spammy affiliate pages on it. I don't build links to it, that takes too much time and investment... instead I just submit a sitemap to google and move on.

That's the short story. The long story is that I built hundreds of thousands of these sub domains for each service of this type I could find, on every one of the domains they made available. Over the course of time it became clear that the performance (measured in google search visitors) was VASTLY different based on the primary domain... to the point that I stopped building for all of them and focused on only a handful of highly performant and profitable domains.

I eventually stopped all of this because it caught the attention of some of the major retailers - I was out ranking jcpenny on their own products on subdomains/pages that had only been published for a couple days. They contacted my affiliate programs, you can imagine where that led. (I don't want to in any way impress that _every_ subdomain or page ranked that well - but it happened enough that it caused serious problems and I left the spam SEO world)

If domain authority is a myth, 1) why did my pages ever get any visitors with no links? 2) Why was the performance so vastly different dependent on the primary domain?

Also - this is still the case today. I'm still in Skype group chats with people who are still doing this same thing. It's always a cat and mouse game with google's spam team, but at the end of the day the same stuff still works.

That's completely invalid. A page with on a domain with a higher authority will almost always outrank one with lower DA, provided all the other variables are the same (esp. content length)

This is becoming even more true post an August update that seems to focus on "brands" (i.e. trusted domains), especially for medical, health and money related keywords

Can’t Google do manual penalties for some sites? How hard would it be for them to do manual bonuses for the top 100 sites in the world. That would be pretty much equivalent to domain authority, and I expect Google is doing just that.

> the concept of domain authority doesn't exist.

Is that really the case now? It's been 3-4 years since I was involved in SEO, and it was very much a thing back then.