Each year, Google changes its search algorithm up to 500 – 600 times. While most of these changes are minor, every few months Google rolls out a “major” algorithmic update that affect search results in significant ways.
For search marketers, knowing the dates of these Google updates can help explain changes in rankings and organic website traffic. Below, we’ve listed the major algorithmic changes that made the biggest impacts on search. Understanding these updates can help with search engine optimization.
See the change history details on SEOMOZ.