This is the companion site to a study Mozilla ran on browser fingerprinting. With the help of almost 25 million Firefox release users, we measured how identifiable browsers really are, found which characteristics make them unique, and used that to design the fingerprinting protections that shipped in Firefox 143. Here you can read the paper and its key findings, browse the full appendix data the PDF had no room for, download the privacy-preserving aggregate data and analysis code, learn how the data was collected, and run an interactive test that compares your own browser against the measured population. If you have a question the data could answer, there is also a discussion board for proposing follow-up research.