Joe Hall asked on Twitter a question many SEOs are wondering, what triggers Google to conduct a manual review of a web site for a manual action penalty?
Google's Gary Illyes was the only Googler to reply to the question, basically saying, no - he won't say:
@rustybrick nope @joehall @Marie_Haynes @JohnMu
— Gary Illyes (@methode) June 25, 2015
But of course, we can speculate.
The obvious review is triggered when someone submits a reconsideration request. But before that, what may trigger it?
Well, we know Google is constantly hunting down link networks, so they can quickly find all the patterns in a network and review those manually quickly.
The others may be triggered via spam reports that any user can submit. Or public outings on blogs, social media, news and more.
Others speculate via disavow files, maybe linkages to spammy sites in Google Webmaster Tools (Search Console) and Googlers just stumbling on sites.
What do you think are the number one and two ways Google is triggered in reviewing a site?
Forum discussion at Twitter.
Update: I was unfair with my story headline and tone of this post. If you look, it wasn't that Google's Gary Illyes would not say, it is that he doesn't know. So that was my mistake. Gary said later on that he will look into what he can find out. Meanwhile, John Mueller responded with these three videos that share some insight: