I don't know how many folks will see this, and of those that do I don't expect many will necessarily be moved by what I say here. I'm going to say it anyways, however, and then I may never look at this thread again. I'm the person who designed the download token scheme that is discussed in this article, and, while I understand all of the concerns and suspicions, I believe that the way we designed this and the way we handle our telemetry data means that this is not the privacy violation some of you are claiming it is. Also, to be clear, I am speaking for myself here, these are my own thoughts and opinions, and I am not representing Mozilla in any official capacity.

So, a download token is a UUID associated with a unique download event. It gets generated when you click the 'download' link, added to the installer, and then passed through to the installed browser. It is returned to us in the telemetry pings that the browser sends back to our telemetry ingestion endpoints. When the download happens, on the server side we capture the download token and the GA session ID and store those in a table. There is nothing else stored in this table.

Having access to this table means that you can correlate the user's activity on the Mozilla website that GA provides with the telemetry data that Firefox sends us. The website activity contains URLs that the user visited, so we consider this "category 3" data (see https://wiki.mozilla.org/Data_Collection#Data_Collection_Cat...), quite sensitive. For that reason this table has highly restricted access, only a small number of individuals are able to get to it.

Access restrictions offer no protection against subpoenas, of course. But I believe you can safely maintain your anonymity by opting out of our telemetry gathering, because when you opt out of telemetry we delete all of the historical telemetry data we have collected for your Firefox profile. Everything, including all of the records that contain the download token.

If this happens, all we are left with is that original record with the download token and a GA session. The download token can no longer be correlated with your telemetry data, and we have no way of associating your Firefox installation with your GA session, not even under subpoena. And this is all assuming that you haven't blocked GA, or that you haven't specified 'Do Not Track' before visiting our website. If you've done either of those things, we won't have a GA session ID for you to begin with.

Oh, incidentally, we never store any IP addresses or other PII in our telemetry data. That all gets scrubbed during ingestion.

Again, I don't expect this to have much impact, but I'm sharing what I know to counter some of the more extreme claims that this removes the ability for Firefox users to remain anonymous.

Finally, we have the obvious question: Why we would even do this? Believe it or not, understanding your user base does actually have some value in serving that user base. For most of Firefox's existence, there has been no trustable feedback loop. Sure, folks out there in the world have opinions, and share them, but opinions differ, and anecdotes are not data. If one person thinks most users will like a particular change, and someone else thinks they won't, nobody can prove their point in any meaningful way. The folks making decisions about Firefox have been flying blind. And, as many of you in this thread have pointed out, it hasn't necessarily been going that well.

In Firefox's early years, there was lots of low hanging fruit, and the competition was a poorly maintained Internet Explorer, so it was easy to win a bunch of market share. Then Chrome came on the scene with their effectively limitless budget and famously data driven product process. We'll never match their budget, but we can try to make choices based on data instead of just letting whoever has the most organizational power decide. My team has spent the last few years building out a data infrastructure that we hope will support better decision making going forward while still trying to honor user privacy and choice. This is a tough balance to strike, and we're far from perfect, but we do our best.

You can learn about or data collection infrastructure and policies in great detail on our docs site (https://docs.telemetry.mozilla.org/index.html), and you can see nearly all of the code that handles our data ingestion and processing in our public repositories (https://github.com/mozilla/gcp-ingestion and https://github.com/mozilla/bigquery-etl).