how accurate is google analytics actually
its no secret that google analytics leaks data and underreports almost every single data points.
last year andy crestodina from orbit media did a research, they compared some real conversions, and a 3rd party analytics data head to head with ga4 data.. google analytics consistently underperformed on average 11%-20%..
working at user maven, we see this all the time too.. sometimes its on a granular level, sometimes through the roof.. we had one of our users do the exact same experiment on one of his landing pages, the result was - 76 (ga4) vs 281 (our tool), thats about 269% discrepancy.
here are some major reasons google analytics is struggling so much to get data:
- ad blockers
- do not allow cookies (through a consent banner)
- browser privacy settings (and incognito mode)
- cookies disabled (browser-level)
- firewall restrictions (within corporate networks)
- and many others
and honestly this is getting worse.. browsers like firefox, safari and brave now block ga by higher margin, and people are getting way more serious with declining cookies.. the gap that was 20-30% a year ago is probably wider today..
if you want to check this yourself its pretty simple..
just open ga4 and any other analytics tool (pre installed on your site) side by side, same date range, same page, look at unique visitors.. takes 10 minutes and the difference will probably surprise you..
if you're using google analytics, do consider comparing it with any other analytics to see the difference head to head.. or just assume the real numbers are around 20% - 30% more.