What does mod_pagespeed beacon do?

Question

What is mod_pagespeed beacon?

I am getting a 404 error on Akamai on this.

I want to know why the module is being used. I would be able to disable it if I knew what it was being used for.

Answer 1

Beacon

Certain filters need to determine things about the page: in particular, the lazyload_images, inline_preview_images, and inline_images filters need to determine which images are above the fold, and the prioritize_critical_css filter needs to determine the CSS actually used by the page.

To do this, the filters inject JavaScript into the rewritten HTML that analyzes the page in the browser and sends data back to mod_pagespeed using a POST method. The default target is /mod_pagespeed_beacon but that can be changed using the ModPagespeedBeaconUrl directive.

Completely disable beacon

<Location /mod_pagespeed_beacon>
    Order allow,deny
</Location>

Answer 2

In servers where mod_pagespeed module is enabled, pages that are processed by this module send a sort of "ping" back to the server. The mod_pagespeed module is used to optimize, compress and cache media or content, so that your users get a better and faster experience on your server.

As far as I can tell, servers do not have to answer this "ping" for the PageSpeed module to work. As such, Akamai probably does not answer to this "ping".

I would advise against disabling PageSpeed module. I use it in all my servers and it really increases website performance.