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:
| VCL | Compute@Edge | |
|---|---|---|
| Availability | General availability | Limited availability |
| Language support | Fastly VCL, a derivative of Varnish Configuration Language | Any language that compiles to WebAssembly (with SDK support for Rust, AssemblyScript, and JavaScript) |
| Invocation | Fastly invokes your code at multiple predefined points in the request-response cycle | Your code handles the entire request-response cycle |
| Commmon capabilities | Edge caching, Logging, Streaming, Request collapsing, Purging, Serving stale, Edge dictionaries, Geolocation & device detection | |
| Unique capabilities | Clustering Shielding Image optimizer Rate limiting Per-response cache settings | General purpose compute Content transformation Async fetch Request composition Parsing and serialization |
| Learn more > | Learn more > | |
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.
Domains, backends, and healthchecks can be configured in multiple ways:
| Domains | Backends | Healthchecks | |
|---|---|---|---|
Using the fastly CLI | fastly domain create | fastly backend create | fastly healthcheck create |
| Using the API | Create domain endpoint | Create backend endpoint | Create healthcheck endpoint |
| Using VCL | Cannot be managed in VCL | backend { ... } declaration | Part of a backend { ... } declaration |
| Using the web interface | See Managing domains | See Managing origins | See 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.
- Controlling cache freshness and TTL
- Deciphering cache hit and miss headers for shielded services
- Purging
- Shielding
- Clustering
- Staleness and revalidation
- Request collapsing
- Segmented Caching
- HTTP/2 server push
- Protected headers
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.
Security
Learn how to configure Fastly to meet your security needs.
- Fastly IP ranges
- Web application firewall
- TLS options
- Detecting TLS connections
- Access Control Lists (ACLs)
Logging, debugging and diagnostics
Observability and debugging tools to help fix problems, test and monitor your Fastly services.