Use Lightning CDN to Load Applications Faster
Salesforce uses a CDN partner to serve the static content for the Lightning Component framework over a CDN. CDNs are the industry standard for web applications because they provide faster and more secure content delivery. A CDN is a geographically distributed network of servers that store cached versions of web assets. To optimize page load times and site performance, a CDN efficiently delivers publicly cacheable content to users.
Lightning CDN is enabled by default for new and existing orgs. When enabled, this setting turns on the Lightning CDN for the static JavaScript and CSS in the Lightning Component framework at the org level. It doesn’t distribute your Salesforce data or metadata in a CDN. Admins can turn off this preference in Setup | Session Settings by deselecting the Enable Content Delivery Network (CDN) for Lightning Component framework checkbox. However, disabling the CDN isn’t recommended because it can impact performance.
If you experience any issues, ask your IT department if your company’s firewall blocks CDN content. Your IT department can make sure that static.lightning.force.com, a.static.lightning.force.com, b.static.lightning.force.com, and *.static.lightning.force.com are added to any allowlist or firewall that your company operates. If you’re using Lightning Out, make sure that Content Security Policy doesn't block a.static.lightning.force.com and b.static.lightning.force.com domains. You can ping static.lightning.force.com but you can’t browse directly to the root URL at https://static.lightning.force.com.