- Aug 17, 2014
- 11,547
Internet users who download the Firefox web browser from the official Mozilla website get a unique identifier attached to the installer that is submitted to Mozilla on install and first run.
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The identifier, called dltoken by Mozilla internally, is used to link downloads to installations and first runs of the Firefox browser. The identifier is unique to each Firefox installer, which means that it is submitted to Mozilla whenever it is used.
While it is possible to download new installers each time a new Firefox version is released, it is also possible to use the downloaded installer again for that purpose.
A bug report on Mozilla's official bug tracking website confirms the use of the download token. The linked document is not public, but the listing itself confirms the use and provides an explanation on why it has been implemented:
This data will allow us to correlate telemetry IDs with download tokens and Google Analytics IDs. This will allow us to track which installs result from which downloads to determine the answers to questions like, "Why do we see so many installs per day, but not that many downloads per day?"
According to Mozilla's description, the identifier is used to analyze downloading and installation trends among other things.
The feature is powered by Telemetry in Firefox and it applies to all Firefox channels.

Each Firefox download has a unique identifier - gHacks Tech News
Internet users who download the Firefox web browser from the official Mozilla website get a unique identifier attached to the installer that is submitted to Mozilla on install and first run.
