Change is the only constant thing in SEO. Even though it is still a relatively new industry, it is estimated that Google updates its algorithm on a daily basis, so the underlying rules change roughly 365 times each year. But rest assured as it is only the major updates that will impact us the most and that is what we will keep keeping tracking here as well. If you are interested in the full details, you can read more over at Rand Fishkin's Moz Site.
"Fred" Update — March 8, 2017
Google rolled out a major update, with reports of widespread impacts across the SEO community. When asked, Gary Illyes of Google jokingly referred to as "Fred" update and the name has been stuck ever since.
Penguin 4.0 (Real time) - 23 September 2016
After a much-awaited 2-year gap, Google has rolled out Penguin 4.0. This will be the last update in Penguin as it will now run in real-time and is also more granular.
Unnamed Update (aka John Doe update) - 8 January 2016
Google introduced an update but details remain sketchy on what is it all about. They only confirmed it as a "Core Algorithms Update".
RankBrain - 26 October 2015
Google introduced a new ranking signal called RankBrain, which uses machine learning and artificial intelligence to deliver better search results. This covers all languages and is mainly used for the 15% of everyday search queries which Google hasn't seen before.
Panda 4.2 Update - 17th July 2015
Another Panda Update was officially confirmed . The only difference this time was that it was a slow roll out, and took as long as a couple of months. Learn more about it here.
Mobile Friendly Update - 21th April 2015
Google made an official update announcement on their Google Webmaster Blog. This change affected mobile searches in all languages worldwide and also had a significant impact on mobile search results.
Penguin 3.0 - 17th October 2014
Google launched another Penguin refresh. This update appeared to be smaller than expected (<1% of US/English queries affected).
Panda 4.1 - 23th September 2014
Google announced another significant Panda update, which included an algorithmic component. It was estimated to affect around 3-5% of queries.
Pigeon - 24th July 2014
The Pigeon update focused on local SEO to dramatically alter some local results and modify how they handle and interpret location cues.
Hummingbird - 24th August 2013
The Hummingbird update was a major overhaul to the all-important concept of semantics, or meaning. It was rolled out to combat the increasing longer search queries key in searches.
Penguin - 24th April 2012
The Penguin update was a major algorithm that targeted sites spamming its search results, in particular those doing so by buying links or obtaining them through link networks designed primarily to boost Google rankings.
Panda - 23th February 2011
The Panda update was a major algorithm update which hit sites hard, affecting up to 12% of search results (a number that came directly from Google). Panda is mainly focused on low-quality (thin) content, sites with high ad-to-content ratios, and a number of other quality issues.
Caffeine - June 2010
The Caffeine update was a refreshment to Google's infrastructure which not only boosted Google's raw speed, but integrated crawling and indexation much more tightly, resulting in (according to Google) a 50% fresher index.
Big Daddy - December 2005
The Big Daddy update was an infrastructure update which changed the way Google handles URL canonicalization, redirects (301/302) and other technical issues.
Florida - November 2003
The Florida update was the death of low-value late-90s SEO tactics, such as keyword stuffing.