mm 5 means Inference
The match was inferred from signals such as IP address and user agent across browsers or devices, without authentication.
When to send it
Use 5 when the ID was attached through probabilistic or graph-based linking: shared IP addresses, user agent features and similar signals tying a browser or device to an ID seen elsewhere. Name the provider in EID.matcher and set EID.mm to 5. This is the honest value for most household and cross-device graphs that work without logins.
Buyers usually discount inferred matches and may restrict them for privacy reasons, since the user never supplied the link. The value is confused with 3 (Authenticated), especially for ID products that mix login-based and inferred matches in one namespace; label each request by how that particular match was made. A person-based UID.atype 3 does not make an inferred match authenticated.
Example
{
"user": {
"eids": {
"mm": 5
}
}
}Fields that carry it
Other values in id match methods
The id match methods list page explains the whole list and its common mistakes.