Learn to build on the Fastly platform

Fastly offers two types of edge services: highly performant and configurable services powered by Fastly VCL, and next generation Wasm-powered Compute@Edge services:

AvailabilityGeneral availabilityLimited availability
Language supportFastly VCL, a derivative of Varnish Configuration LanguageAny language that compiles to WebAssembly (with SDK support for Rust, AssemblyScript, and JavaScript)
InvocationFastly invokes your code at multiple predefined points in the request-response cycleYour code handles the entire request-response cycle
Commmon capabilitiesEdge caching, Logging, Streaming, Request collapsing, Purging, Serving stale, Edge dictionaries, Geolocation & device detection
Unique capabilitiesClustering
Image optimizer
Rate limiting
Per-response cache settings
General purpose compute
Content transformation
Async fetch
Request composition
Parsing and serialization
Learn more >Learn more >
Whichever service type you choose, many concepts are common. And while not all Fastly features are supported by Compute@Edge yet, many more will be added in the coming months as we move towards general availability.

Domains and backends

Domains are hostnames that point to your services on Fastly. Backends are hostnames that point to the origin servers hosting your application. Healthchecks are pre-configured requests that Fastly POPs should make, to your backends, to confirm that they are ready to receive end user traffic.

Illustration of domains and backends

Domains, backends, and healthchecks can be configured in multiple ways:

Using the fastly CLIfastly domain createfastly backend createfastly healthcheck create
Using the APICreate domain endpointCreate backend endpointCreate healthcheck endpoint
Using VCLCannot be managed in VCLbackend { ... } declarationPart of a backend { ... } declaration
Using the web interfaceSee Managing domainsSee Managing originsSee Working with health checks

Routing and caching

Fastly respects the instructions you provide via HTTP headers such as Cache-Control. But you can also exert much finer-grained control over the way we load and cache your resources.

Content transformation

As well as serving content loaded from your origin, Fastly can also manipulate that content in useful ways, or even generate content from scratch without loading anything from your origin.

Edge state and data stores

Our edge state products allow reads at the edge and updates via the API.


Learn how to configure Fastly to meet your security needs.

Logging, debugging and diagnostics

Observability and debugging tools to help fix problems, test and monitor your Fastly services.