Here is the best way to report on session duration for each session in GA4

To create a report on session duration in GA4, follow these steps:

1. Create a blank exploration report in your GA4 property.
2. Add the 'Stream name' dimension to the report.
3. Add the 'Average session duration' metric to the report.
4. Change the visualization to a 'Line chart'.
5. Set the 'GRANULARITY' to 'Day' to view the data on a daily basis.
6. Enable the 'ANOMALY DETECTION' setting to identify and display outliers in your data trend, which appear as small circles on the line chart.
7. Adjust the 'TRAINING PERIOD (DAYS BEFORE TIMEFRAME)' under 'ANOMALY DETECTION' to the maximum for improved accuracy in anomaly detection.
8. Increase the 'SENSITIVITY' under 'ANOMALY DETECTION' to the maximum to detect and report more anomalies in your data trend.

The purpose of 'ANOMALY DETECTION' in GA4 reports is to identify and display outliers in your data trend. When this setting is turned on, anomalies appear on the line chart in the form of small circles, allowing you to easily spot unusual fluctuations in session duration that may require further investigation.

To increase accuracy in anomaly detection in GA4, you should:

• Change the 'TRAINING PERIOD (DAYS BEFORE TIMEFRAME)' under 'ANOMALY DETECTION' to the maximum. A longer training period allows the system to learn from a broader set of data, improving its ability to accurately detect anomalies.

• Adjust the 'SENSITIVITY' setting under 'ANOMALY DETECTION' to the maximum. Higher sensitivity means the system will be more likely to detect and report anomalies, although this may also increase the number of false positives.