Fastly VCL | Fastly Documentation

Network services
Customize your content delivery.
Full-Site Delivery (CDN)
Streaming Delivery
Purging
Image Optimizer
Security
Protect your services and applications.
Next-Gen WAF
Edge Rate Limiting
Access Control Lists
TLS
Compute
Experiment with Fastly's edge computing platform.
Compute services
Testing and debugging
Edge Data Storage
Quick start
Go from zero to Fastly with these step-by-step guides and tutorials.
CDN getting started guide
Compute getting started guide
Building blocks
Start with the basics and learn how Fastly lets you take advantage of the modern internet.
Services
Core concepts
Web interface guides
Integrations
Find out how Fastly services interoperate with non-Fastly services.
Streaming logs
Logging endpoints
Non-Fastly services
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Tutorials
Step-by-step guides to developing with Fastly
Deliver a site with Fastly
Enhance your UX with Compute
Edge deploy Next-Gen WAF
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Demos
Discover how Fastly can enhance your user experience.
Passwordless auth
Fanout chat
Social sharing cards
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Use Cases
Get solutions to specific problems with curated topics.
Authentication
Geolocation
Personalization
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Code Examples
Try out Fastly code in the browser and easily remix it for your own project.
Geolocation at the edge
Optimize images on the fly
Redirect URLs at the edge
See all code examples
Starter Kits
Start developing your project immediately with Fastly from a functional template.
Rust default starter
JavaScript default starter
Go default starter
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About Fastly VCL

Fastly VCL is a domain-specific programming language that evolved from the Varnish proxy cache , forming a core part of Fastly's…

Getting started with VCL

Customize your content delivery.

Working with custom VCL

Fastly allows you create your own Varnish Configuration Language (VCL) files with specialized configurations. By uploading custom VCL…

VCL best practices

Best practices in Fastly VCL have changed over time to help address expectation gaps and improve maintainability. This page covers some of…

VCL regular expression cheat sheet

Fastly VCL uses a subset of Perl Compatible Regular Expression (PCRE) syntax. This is case sensitive and forward slashes don't need to be…

Clustering in VCL

In normal operation, a request directed to a Fastly POP will be handled by two separate cache servers acting together in a process we call…

Synthetic errors in VCL

If a fatal error occurs in your service while processing your VCL logic, Fastly will generate an error response with a 503 HTTP status…

These articles describe VCL Snippets and how to use them.