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Version: 3.13.0


The env() function returns the value for the provided environment variable name.

For a list of available environment variables, see the Fastly Developer Hub for Compute Environment Variables

Note: The environment variables can only be retrieved when processing requests, not during build-time initialization.




  • name : string
    • The name of the environment variable to retrieve

Return value

The value for the requested environment variable, if no such environment variable exists then an empty string is returned.


In this example we log to stdout the environment variables FASTLY_HOSTNAME and FASTLY_TRACE_ID.

/// <reference types="@fastly/js-compute" />
import { env } from "fastly:env";
function app(event) {
console.log("FASTLY_HOSTNAME:", env("FASTLY_HOSTNAME"));
console.log("FASTLY_TRACE_ID:", env("FASTLY_TRACE_ID"));
return new Response("", {
status: 200
addEventListener("fetch", event => event.respondWith(app(event)));