Difference under 10% between IO and GA as well as with other analytics tools is natural.
Here are the most common reasons why the difference can be more significant:
- Difference in setup. Endless scroll, galleries, sliders can be tracked differently by different systems.
- Codes were not added to all the platforms: mobile version of the website, AMP or Instant Articles, mobile app.
- Comparing different metrics. Make sure you compare pageviews to pageviews, uniques to uniques, etc. Also make sure you select equal timeframes while comparing data.
- Different logic. Sometimes it is not a discrepancy, it is how it should be. For example Real time tracking in GA and in IO (*link to an article about this*).
If the difference is more than 10%, you feel uncomfortable with the data and not sure if your case is one of the listed - please let us know. We will do our best to find the reason.