How much data is missing from Google Analytics due to adblockers?

I looked at the analytics of a website that had a post trending on Hacker News and Reddit last week with more than a thousand upvotes and more than a thousand comments. The idea was to find out how much data is missing from Google Analytics due to adblockers and privacy-friendly browsers that the more tech-savvy audiences use more frequently.

I compared stats between Plausible Analytics (the startup that I'm working on) and Google Analytics. Google Analytics was installed using the default method. Plausible was installed using a proxy to get the most accurate data on the level of blockage. Plausible proxy runs as a first-party connection and is only blocked by those visitors who block JavaScript entirely. It is not blocked by any browser or adblocker.

Here’s the data Plausible Analytics shows for the three days in late August 2021 when the site got a lot of traffic (you can explore the stats in this public dashboard):

And here’s the Google Analytics data for the same site and the same period:

It turns out 58% of Hacker News readers, Reddit users and other techies block Google Analytics. Google Analytics is not showing all traffic. It is missing data from 58.67% of all visitors and 58.38% of all page views. Google Analytics is underreporting the tech-savvy audiences by almost 60%.

Which browser users block Google Analytics most frequently?

88% of Firefox users
50% of Chrome users
41% of Safari users

Which operating system users block Google Analytics most frequently?

82% of Linux users
74% of Windows users
61% of Mac users
54% of Android users
41% of iOS users

More stats and other details in the blog post: 58% of Hacker News, Reddit and tech-savvy audiences block Google Analytics