Alan Bleiweiss, a smart and fun SEO, asked John Mueller of Google if Google has a "Google Book of Secrets" where it stores all the algorithmic changes it makes in a single location. The short answer is, yes, Google does store all the changes it makes but the long answer from John is that it isn't always useful.
The question came up at the 38:26 mark where Alan asked "does Google have someone tasked with the job of recording each update in a log book, and noting which aspects of search are impacted? If so, is it called "Google's Book of Secrets"?"
John Mueller said that yes, Google does document all of the changes it makes but he added that it is hard, even for internal Google purposes, to use that to figure out why a change happened to a specific URL. John said "it is really hard sometimes to track back, even on our side, which of the changes had an effect here and what caused this difference in rankings."
Mueller added that even if Google did publish this, which they kind of did in the past, it wouldn't be helpful. John said "so even if we gave you this kind of log book of Google Search change, I think it is really hard to turn that into something useful."
Here is how John answered the question:
I don’t know, Alan. I don’t really have a good answer for you there. We do track the changes we make and we try to figure out what all is changing over time. But there are lots of things that are changing in search and sometimes it’s hard to track back. Because these things are approved at some point and launched at some point and when you look at an individual URL and you see changes there, it is really hard sometimes to track back, even on our side, which of the changes had an effect here and what caused this difference in rankings.So even if we gave you this kind of log book of Google Search change, I think it is really hard to turn that into something useful. And then say now that I know Google made this change, I will always be updating my site to match that because you can’t really do the reverse of that.
Here is the video embed so you can watch it yourself:
Forum discussion at YouTube Community.