The 'New engagements' metric shows the number of times a visitor matches a marketing channel for the first time in that visitor's engagement period. This metric is useful when you want to compare any dimension with a visitor matching a marketing channel processing rule for the first time.
How this metric is calculated
During data processing, every hit runs through Marketing channel processing rules . If a hit matches any marketing channel processing rule and the visitor does not already have a first touch channel, the hit is a new engagement. If a hit does not match any marketing channel processing rules or if the visitor already has a first touch channel, the hit is not a new engagement.
Visitors can have more than one new engagement if they let their visitor engagement period expire.