Reference documentation
Welcome to the Fastly reference library. Here you'll find comprehensive technical detail about the interfaces exposed by the Fastly platform and products, including complete syntax and examples for functions, variables, CLI commands, and API endpoints.
Our Compute platform runs WebAssembly binaries compiled from your own code. Find out more about our official SDKs, environment variables and more.
Via the Fastly API you can perform any of the operations that are possible within the management console, including creating services, domains, and backends, configuring rules or uploading your own application code, as well as account operations such as user administration and billing reports.
Use the Fastly CLI to manage services, scaffold out local development environments and compile your Compute projects, among a host of other useful features.
Fastly provides numerous libraries and tools that help simplify the setup, testing, validation and deployment of your code.
Fastly respects standards in our implementations of HTTP, but in some cases there are nuances in our implementation, or extensions to the standards.
Fastly's Next-Generation Web Application Firewall (NGWAF) is a modern, edge-native WAF that protects your web applications from a variety of threats.
The Fastly Image Optimizer (IO) allows images to be transformed, resized, and optimized on the fly as they move through the Fastly edge cloud. Use IO query parameters to control the behavior of the optimizer.
Terms relating to Fastly technology and services.
Most pages on the Fastly documentation site are available in Markdown format, making it easy for AI assistants, large language models (LLMs), and developer tools to consume technical content.
Set up AI coding agents such as Claude Code, Codex, and Cursor with the Fastly Agent Toolkit and up-to-date Fastly documentation. For agents that can't run commands, use the Fastly MCP server.
This changelog provides information on changes across the Fastly platform, including to the VCL language, our public API, CLI, Terraform provider, and Compute SDKs.
Our VCL platform evolved from Varnish 2.1.5 and supports a heavily modified and extended variant of Varnish Configuration Language (VCL) for programming custom, high performance edge logic on our CDN services.
