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Connect to Workers and Bindings

Containers can access Workers bindings — KV, R2, D1, Durable Objects, and others — through outbound handlers. An outbound handler intercepts HTTP requests from the container and runs inside the Workers runtime, where all of your configured bindings are available.

The container makes a plain HTTP request to a virtual hostname (for example, http://my.kv/some-key), and the outbound handler resolves it using the bound resource. No SDK or client library is required inside the container.

Use bindings in outbound handlers

Define an outboundByHost handler for each virtual hostname. The env argument gives you access to every binding declared in your Wrangler configuration.

JavaScript
export class MyContainer extends Container {}


MyContainer.outboundByHost = {
  "my.kv": async (request, env, ctx) => {
    const url = new URL(request.url);
    const key = url.pathname.slice(1);
    const value = await env.KV.get(key);
    return new Response(value);
  },
  "my.r2": async (request, env, ctx) => {
    const url = new URL(request.url);
    // Scope access to this container's ID
    const path = `${ctx.containerId}${url.pathname}`;
    const object = await env.R2.get(path);
    return new Response(object?.body ?? null, { status: object ? 200 : 404 });
  },
};

The container calls http://my.kv/some-key and the handler resolves it using the KV binding. A call to http://my.r2/file.png reads from R2, scoped to the current container instance.

Access Durable Object state

The ctx argument exposes containerId, which lets you interact with the container's own Durable Object from an outbound handler.

JavaScript
"get-state.do": async (request, env, ctx) => {
  const id = env.MY_CONTAINER.idFromString(ctx.containerId);
  const stub = env.MY_CONTAINER.get(id);
  // Assumes getStateForKey is defined on your DO
  return stub.getStateForKey(request.body);
},