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
See all guides
Tutorials
Step-by-step guides to developing with Fastly
Deliver a site with Fastly
Enhance your UX with Compute
Edge deploy Next-Gen WAF
See all tutorials
Demos
Discover how Fastly can enhance your user experience.
Passwordless auth
Fanout chat
Weather app
See all demos
Use Cases
Get solutions to specific problems with curated topics.
Authentication
Geolocation
Personalization
See all use cases
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
See all starter kits

req.is_esi_subreq

BOOL, read-only.

Available inall subroutines.

Whether VCL is being evaluated within an ESI fragment.

Network services

Security

Compute

Quick start

Building blocks

Integrations

Tutorials

Demos

Use Cases

Code Examples

Starter Kits

req.is_esi_subreq