DuckDuckGo asked participants in the study to conduct identical searches at the same time. It found:
Most participants saw results unique to them. These discrepancies could not be explained by changes in location, time, by being logged in to Google, or by Google testing algorithm changes to a small subset of users.
On the first page of search results, Google included links for some participants that it did not include for others, even when logged out and in private browsing mode.
Results within the news and videos infoboxes also varied significantly. Even though people searched at the same time, people were shown different sources, even after accounting for location.
Private browsing mode and being logged out of Google offered very little filter bubble protection. These tactics simply do not provide the anonymity most people expect. In fact, it’s simply not possible to use Google search and avoid its filter bubble.