Adding `traffic-advice` File to Apache2 Server

Adding `traffic-advice` File to Apache2 Server

2025-06-01
Linux

On my web server, I was seeing a lot of 404 errors like the one below:

142.250.32.36 - - [22/May/2025:02:47:35 -0400] "GET /.well-known/traffic-advice HTTP/1.1" 404 4259 "-" "Chrome Privacy Preserving Prefetch Proxy"

After some googling, I came up with the following solution.

  1. Create a JSON file /var/www/traffic_advice.json with the following content:
[
  {
    "user_agent": "prefetch-proxy",
    "google_prefetch_proxy_eap": {
      "fraction": 0.9
    }
  },
  {
    "user_agent": "Chrome Privacy Preserving Prefetch Proxy",
    "google_prefetch_proxy_eap": {
      "fraction": 0.9
    }
  },
  {
    "user_agent": "*",
    "accept": {
      "purpose": {
        "prefetch": true,
        "prerender": true
      },
      "sec-purpose": {
        "prefetch": true,
        "prerender": true
      }
    }
  }
]

The location is not important; in my case it happened to be root directory for all sites.

  1. Create the following Apache2 configuration file etc/apache2/conf-available/traffic-advice.conf:
# Global traffic-advice configuration
Alias "/.well-known/traffic-advice" "/var/www/traffic-advice.json"

<Files "traffic-advice.json">
    # Set the appropriate headers
    Header always set Content-Type "application/trafficadvice+json"
    Header always set Permissions-Policy "browsing-topics=(), prefetch=()"
</Files>

Make sure the file location on the Alias line matches the location of the traffic-advice.json file.

  1. Enable the Apache2 headers module:
$ sudo a2enmod headers
$ sudo systemctl reload apache2
  1. Enable the newly created configuration:
sudo a2enconf traffic-advice
sudo systemctl reload apache2
  1. Use curl to verify the server response:
curl -i https://neacsu.net/.well-known/traffic-advice
HTTP/1.1 200 OK
Date: Sun, 01 Jun 2025 16:58:32 GMT
Server: Apache/2.4.41 (Ubuntu)
Content-Type: application/trafficadvice+json
Permissions-Policy: browsing-topics=(), prefetch=()
Last-Modified: Sun, 01 Jun 2025 16:47:43 GMT
ETag: "19c-6368567f7b9ac"
Accept-Ranges: bytes
Content-Length: 412

[
{
  "user_agent": "prefetch-proxy",
  "google_prefetch_proxy_eap": {
    "fraction": 0.9
  }
},
{
  "user_agent": "Chrome Privacy Preserving Prefetch Proxy",
  "google_prefetch_proxy_eap": {
    "fraction": 0.9
  }
},
{
  "user_agent": "*",
  "accept": {
    "purpose": {
      "prefetch": true,
      "prerender": true
    },
    "sec-purpose": {
      "prefetch": true,
      "prerender": true
    }
  }
}
]

References #

  1. lexo.ch - .well-known/traffic-advice : Optimizing Website Performance, reducing Server Load and 404 errors: Optimal Browser Prefetch Management
2025-06-01