Lighthouse: Use a Content Delivery Network (CDN)
Using a "Content Delivery Network (CDN)" can improve your site performance across different global regions.
When a user visits your page, the resources are served from the cache of the closest CDN node, instead of your origin server, reducing latency and providing a fast page experience to your visitors wherever they are located.
How does your site score on this audit?
How does using a Content Delivery Network (CDN) affect page performance?
A Content Delivery Network reduces latency by caching your page's static resources across different servers around the world.
Depending on where your visitors are located, your page content is served from the closest server/CDN node.
CDNs may also improve your page performance in other ways.
How does GTmetrix trigger this audit?
GTmetrix looks at the response headers of your page requests and identifies the ones that aren't served from a known CDN.
If your page has static resources that aren't on a known CDN, GTmetrix triggers this audit. This audit's impact score will depend on how many resources aren't served from a known CDN.
Note that this audit has a lesser impact on your Structure Score and will more likely influence your Performance Score.
This is a Custom GTmetrix audit
Use a Content Delivery Network (CDN) isn't originally included in the default Lighthouse list of audits. However, given its potential impact on performance, we felt it was important enough to include in our implementation of Lighthouse in GTmetrix.
CDNs provide significant performance gains for your visitors on a global basis. No matter where your visitors originate from, a CDN can ensure consistent performance by serving static resources from a server node closest to them.
We appreciate that not all websites require CDNs, and thus the Use a Content Delivery Network (CDN) audit is not as punishing to your Structure Score as it once was in our Legacy Reports; however, it will still impact it to some degree.
How to fix this audit?
Firstly, CDNs are not essential to your website functionality.
While they can significantly improve your website performance across different geographic locations, the question of whether you should use one depends on your target audience and your performance goals.
Consider the following scenarios:
1) Recognized CDNs
If you choose a popular CDN (e.g., Cloudflare, Netflify, Amazon CloudFront) to serve your page resources, GTmetrix may already recognize this CDN. In that case, this audit should get fixed once you start using the CDN.
2) Unrecognized CDNs
If you're using a CDN that is uncommon and/or not recognized by GTmetrix, reach out to us and we'll review for inclusion.
3) I don't need a CDN
If you strongly feel that you don't need to use a CDN for good reasons (e.g., local audience, small website, etc.), you can bypass this audit by adding your domain to the CDN hostnames field under Analysis Options on your Account page.
When done so, GTmetrix will not penalize your website for lack of CDN usage. However, note that Performance Score will see no change.