Alt-Svc Header

An Alternative Services (Alt-Svc) header can be sent by your origin server to tell a requesting client that another service can be used for future requests. Among other things, this can help improve traffic manageability and efficiency.

How it works

This behavior works in conjunction with the HTTP/3 behavior in your property. When you add that behavior to your property, ​Akamai​ automatically generates the Alt-Svc header for requests and sets the max-age (ma) for it to 93600 seconds.


You don't need to include this behavior to support an Alt-Svc header. You only need to add it if you want to change the ma.


Add this behavior to a rule in your property that will also apply to a rule that's using HTTP/3. Only include it if you want to set the ma to a value other than the default of 93,600 seconds. You can input a value from 1 to 214,748,647 seconds.

Example scenarios

For example, you could:

  • Add it to the Default Rule. If you've set HTTP/3 in the Default Rule, this will set a different ma for all requests.

  • Add it to a child rule if HTTP/3 is in the Default Rule. For example, If you're using multiple hostnames and you want to change the ma for requests from one of those hostnames, and you want to use the default value for all other requests.

  • Add it to a custom rule with HTTP/3 Support. For example, if you have multiple hostnames in your property and you only want to apply HTTP/3 Support for requests from a specific hostname. Set up HTTP/3 in the custom rule using the desired hostname and include the Alt-Svc Header behavior. All requests from that hostname will use the HTTP/3 and the ma set in the Alt-Svc Header behavior.

Caveats and requirements

Consider these points if adding this behavior:

  • You can't use this behavior in your property if you're not using HTTP/3.
  • Your behavior can only have one instance of the HTTP/3 behavior.