The biggest cause of discrepancies between for two analytics systems on the same website, is the users that leave before a page has finished, and one analytics system has loaded but the other has not yet. Discrepancies of a few percentage are reasonable. If there is a large discrepancy (like 10% or more) you need to investigate.
The reasons for discrepancies can include:
- Accidental clicks
- People hit stop before the page has loaded, or close the tab
- People load the page but the analytics didn’t load before they left
- Too many scripts loaded by the destination page
A reasonable click discrepancy is >15%. If it is a lot higher you may want to adjust your campaign, either the settings, the creative or the destination page.
High discrepancies can be caused by:
- Slow page speed, make sure your page is fast to load.
- Mobile clicks, users tend to cancel more, experience slower network and/or leave before the page loads.