Google Analytics may sometimes show less results than visible on Facebook for the same campaign. This can have multiple reasons, of which the most regular are listed below.
Cookie-based vs. non-cookie-based tracking methods
Since Google Analytics is a cookie-based analytics program, cookies need to be enabled to report a visit to a page. Visits with cookies disabled are not reported. Non-cookie-based tracking software does not have this drawback and can therefore report more visits.
Google Analytics limits a site visit to once every 30 minutes per visitor. Facebook does not use this limit and thus can report multiple visits per unique user within the 30 minute time-frame.
Clicks vs. Visits
Google Analytics measures the visits to a page, while Facebook measures the click that precedes visiting the site. So, when a user clicks your ad multiple times and opens your site multiple times within the 30 minutes time-frame, this will be reported in Facebook as multiple clicks but as only one visit in Google Analytics.
Partial page load
After clicking your ad, the visitor might manually prevent the page from loading fully. If this is the case, the Google tracking code is not able to send information to Analytics. Then, there will be a click in Facebook but no visit will be reported in Analytics.
These are only the most common reasons for the mismatch of the Facebook and Analytics data, there are more: loading a page from the cache, visitors located in different time zones or certain data filters all can affect the dissimilarity of the two report platforms.
To know more about this, you should check out The Next Ad's article in our blog.