A plugin for Winter CMS that adds to the site the page /.well-known/traffic-advice with a JSON response containing instructions for preloading the site in the Chrome browser when it appears in Google search.

composer require webvpf/wn-trafficadvice-plugin

If your site has search traffic from Google, then by turning on “Save failed requests” in the settings, you will see that your site receives a large number of requests for the address https://example.com/.well-known/traffic-advice

This is a Google proxy server that requests instructions for preloading the site, so that when the user leaves the search, the site page loads as quickly as possible.

Instead of instructions, the Google proxy server receives a 404 error, and Winter CMS records an error log (if enabled in the settings).

You can use the traffic advice's fraction field to control how much traffic the Private Prefetch Proxy should let through. You can start with a small fraction such as 0.3 (that is, 30%), and gradually increase it to 1.0 (that is, 100%) by adding the following JSON to a /.well-known/traffic-advice file, which needs to be served with the application/trafficadvice+json MIME type:

[{
  "user_agent": "prefetch-proxy",
  "fraction": 0.3
}]

The fraction field is a float between 0.0 (no prefetch at all) and 1.0 (100% of the prefetch requests get through).

It is also possible to disable this completely with the following configuration:

[{
  "user_agent": "prefetch-proxy",
  "disallow": true
}]

See more details https://developer.chrome.com/blog/private-prefetch-proxy/#traffic