What could be the reason for the sudden surge in Direct channel traffic in GA4?
Spam Traffic
Spam traffic is actually abnormal traffic, usually machine traffic.
You can add dimension information such as geography and device in the secondary dimension. If the metrics are abnormal, it is usually spam traffic, as shown below:
The metrics in the United States are abnormally low, which includes some normal traffic. If normal traffic is excluded, it is estimated that these metrics will become 0.
If your traffic comes from the cities of Des Moines, San Antonio, Moses Lake, and Cheyenne, then estimate the machine traffic. These cities are Azure data centers.
Campaign Traffic is Not Marked with UTM
The campaign diverted traffic and did not mark UTM properly.
For example, if a campaign is used to attract traffic from an APP, but no UTM tag is used, since it is coming from the APP and there is no Referral, it is classified into the Direct channel.
Or if a link is shared in the community without marking it, it will also be assigned to the Direct channel.
Confirm with marketing colleagues whether there has been a recent campaign and whether UTM marking has been done.
CMP installation Error
If you install CMP incorrectly (the full name of CMP is Consent Management Platform), and if the first page tracking is lost, it will cause the traffic that should be allocated to other channels to be mistakenly allocated to the Direct channel.
Check whether CMP has been installed recently and whether CMP is installed accurately.
Bug
If none of those reasons apply, it may be bugs.