Danny Sullivan, Google's Search Liaison, clarified the distinctions between algorithm updates and data refreshes. Algorithm updates, often referred to as core updates, involve significant changes to how Google's systems operate, process signals, and interact with one another. On the other hand, data refreshes involve the systems taking in new data and processing it, which can lead to changes in search results without the system itself being updated.
Sullivan emphasized that search is always being updated due to the ever-changing nature of the web, making it challenging to confirm changes to ranking as a lot of it is real-time data updating. He also mentioned that Google has a status dashboard where significant updates are noted.
This explanation is a condensed version of what former Googler, Matt Cutts, explained in 2006. Cutts described algorithm updates as changes that typically yield larger changes in search results, while data refreshes are less impactful changes often unnoticed by people. He also introduced the concept of an index update, which was a small type of data refresh where new indexing data is pushed out to data centers.
Cutts referred to the period from 2000 to 2003 when index updates happened monthly as the Google Dance. During this time, each data center was taken out of rotation and loaded with a new web index, a process that took 6-8 days. However, in the summer of 2003, Google switched to an index that was incrementally updated daily or faster, resulting in smaller day-to-day changes referred to as everflux. Now, index updates are no longer done, but they remain a significant part of Google's history.
