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Outbound Workers

Outbound Workers sit between your customer’s Workers and the public Internet. They give you visibility into all outgoing fetch() requests from User Workers.

Outbound Workers diagram information

​​ General Use Cases

Outbound Workers can be used to:

  • Log all subrequests to identify malicious hosts or usage patterns.
  • Create, allow, or block lists for hostnames requested by user Workers.
  • Configure authentication to your APIs behind the scenes (without end developers needing to set credentials).

​​ Use Outbound Workers

To use Outbound Workers:

  1. Create a Worker intended to serve as your Outbound Worker.
  2. Outbound Worker can be specified as an optional parameter in the dispatch namespaces binding in a projects wrangler.toml. Optionally, to pass data from your Dispatch Worker to the Outbound Worker, the variable names must be specified under parameters.

Make sure that you have [email protected] or later installed.

binding = "dispatcher"
namespace = "<NAMESPACE_NAME>"
outbound = {service = "<SERVICE_NAME>", parameters = [customer_name,url]}
  1. Edit your Dispatch Worker to call the Outbound Worker and declare variables to pass on dispatcher.get().
export default {
async fetch(request, env) {
try {
// parse the URL, read the subdomain
let workerName = new URL(request.url).host.split('.')[0];
let userWorker = env.dispatcher.get(
{// outbound arguments
outbound: {
customer_name: workerName,
url: request.url}
return await userWorker.fetch(request);
} catch (e) {
if (e.message.startsWith('Worker not found')) {
// we tried to get a worker that doesn't exist in our dispatch namespace
return new Response('', { status: 404 });
return new Response(e.message, { status: 500 });
  1. The Outbound Worker will now be invoked on any fetch() requests from user Workers. The User Worker will trigger a FetchEvent on the Outbound Worker. The variables declared in the binding can be accessed in the Outbound Worker through env.<VAR_NAME>.