Fastly is an American cloud computing services provider. It describes its network as an edge cloud platform, which is designed to help developers extend their core cloud infrastructure to the edge of the network, closer to users.[2] The Fastly edge cloud platform includes their content delivery network (CDN), image optimization, video and streaming, cloud security, and load balancing services.[3] Fastly's cloud security services include denial-of-service attack protection, bot mitigation, and a web application firewall.[4] Fastly's web application firewall uses the Open Web Application Security Project ModSecurity Core Rule Set alongside its own ruleset.

The Fastly platform is built on top of Varnish.[5] As of August 2022, Fastly transfers More than 100Tbps of data.