CDN is the power to accelerate website performance throughout the world. When you only have one Datacenter, CDN makes it available to all countries. Here is the Free CDN list that I have tested.
1. Statically (FREE)
Staticaly is a free multi-CDN for Git repositories, WordPress, images and other assets with high-performance of caching and optimization.
2. Imgpx (FREE)
CDN for images, serve your images with Multi CDN, Auto optimize your images to WebP format.
3. CloudFlare (FREE)
Their DNS is fast.
4. KeyCDN (Free Trial for 30 Days)
Their caching is good, really fast, and I love it, you should try.
5. CDN77 (14 days trial)
Loved their support and custom datacenter, their dashboard also cozy.
6. Fastly (FREE Test Up to $50 of traffic!)
Fastly is my favorite, almost all of my work uses their services.
7. BunnyCDN (they really fast but only 14 days trial)
8. StackPath (30 days trial)
Loved their caching
9. G-Core Labs (14 days for free)
10. jsDelivr CDN (FREE with Multi CDN for GitHub, NPM and WP Plugins)
11. Rawgit (FREE CDN for GitHub only, StackPath network)
12. raw[.]githack[.]com (FREE CDN for GitHub, GitLab, Bitbucket, CloudFlare network)
13. CDN[.]net (Free Trial for 30 Days)
14. Fly[.]io (Edge Application $25 of free credits ) can be used as a CDN.
15. Netlify (FREE All-in-one platform for automating modern web projects, can host your GitHub pages, Gatsby site, Hugo CMS and many more).
16. Zeit (With their Now , Free 100GB Bandwith).
You can choose CDN according to your needs, and hopefully find the best one. Good luck!