CMA Concurrency Demo for Google’s Protected Audience API

The Protected Audiences (PA) specification states that promises are used to fetch perBuyerSignals in section 4.

Each buyer in a PA auction will likely be operating their own domain and will not be sharing them.

There is a limit to the number of concurrent requests to different domains that a web browser can handle. The precise limit will vary between web browsers, operating systems, network, and hardware.

This demo fetches the favicon.ico file from random domains concurrently starting the requests in random order. Favicon.ico is used because many domains host the file, and the file size is roughly the same for every icon. The network traffic is similar to that used with Protected Audiences API. All domains and response times are shown in the table.

This simple demonstration provides the CMA with an expected maximum number of buyers that can participate in a PA auction with a timeout for responses of milliseconds in practice. The true value could be lower as other activities in the web browser, operating system, network, or hardware might also consume the same resources. For example; other activity on the web page, other tabs in the browser, or other applications.


Domain Elapsed Time (ms)