Google's John Mueller explained what he would consider being a search quality issue, causing ranking issues specific to Google considering the site not "quality." John said on Twitter "to me, quality issues are things that users would consider to be problematic."
He added that technical issues that users do not see likely would not be considered a quality issue by Google. John said, "bad rel-canonical leading to an alternate URL being indexed something users would notice? Probably not."
John also said it is common to see both quality and technical issues on the same site but that does not mean the two are the same. John wrote, "both technical issues & quality issues are extremely wide fields, there's always some overlap (eg, is speed a quality or a technical issue?)." "If a site has glaring issues in one of the two, then tweaking the other side won't make a big impression," he added.
Here are the tweets related to this, so you can see it in context:
.@johnmu are SEO technical issues quality issues? I've seen articles that say you said they were and that you said they weren't lol
— Kristine Schachinger (@schachin) September 21, 2022
Just trying to get clarification.
Both technical issues & quality issues are extremely wide fields, there's always some overlap (eg, is speed a quality or a technical issue?). If a site has glaring issues in one of the two, then tweaking the other side won't make a big impression.
— 🌽〈link href=//johnmu.com rel=canonical 〉🌽 (@JohnMu) September 21, 2022
It depends on what you consider a quality issue. To me, quality issues are things that users would consider to be problematic. Is a bad rel-canonical leading to an alternate URL being indexed something users would notice? Probably not.
— 🌽〈link href=//johnmu.com rel=canonical 〉🌽 (@JohnMu) September 21, 2022
And somewhat related but in a different thread, John wrote "Just because a website is technically valid doesn't mean it's a useful & relevant search result for users."
Just because a website is technically valid doesn't mean it's a useful & relevant search result for users.
— 🌽〈link href=//johnmu.com rel=canonical 〉🌽 (@JohnMu) September 21, 2022
So technical issues and quality issues are different, according to John Mueller of Google.
Forum discussion at Twitter.
