User engagement and adoption is typically measured in terms of the number of users active during a given period, generally termed as xAU where x stands for the measurement time interval. Without third-party cookies, it is difficult to obtain xAU measures, especially when content is embedded within other applications and services.
This disclosure describes cookieless techniques to determine a lower bound for various xAU measures. Upon receiving a request for content, a xAU token for the user agent is generated and cryptographically signed on the server and relayed to the user agent for local caching. Each xAU token can be a tuple of the form (period, nonce, cryptographic signature). Once the epoch corresponding to the period in the xAU token expires, the corresponding xAU token is sent back to the server via an out-of-band channel. The number of unique active users per epoch is obtained by counting the number of unique xAU tokens seen over the corresponding epoch. Implementation of the techniques with user permission enables reasonably accurate counts for unique active users during a given period, without requiring the use of third-party cookies.
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Isles, Adrian, "Using xAU Tokens to Count Unique Active Users Per Epoch Without Cookies", Technical Disclosure Commons, (November 01, 2021)