Route fetch through an HTTP proxy
Deno honors the HTTP_PROXY, HTTPS_PROXY, and NO_PROXY environment variables by default, for both module downloads and fetch, with no code changes. When one fetch call needs a different proxy than the rest of the process, Deno.createHttpClient configures a proxy explicitly. This example starts a tiny logging proxy and routes a single fetch through it.
A client talking to an HTTP proxy puts the absolute target URL in the request line instead of just a path. Deno.serve exposes that URL as req.url, so forwarding it with fetch is enough to act as a basic proxy for plain HTTP targets. A real proxy also implements the CONNECT method to tunnel HTTPS traffic, which this handler does not.
const proxy = Deno.serve({ port: 8080 }, async (req) => {
console.log("proxy saw:", req.method, req.url);
const headers = new Headers(req.headers);
headers.delete("host");
return await fetch(req.url, {
method: req.method,
headers,
body: req.body,
redirect: "manual",
});
});createHttpClient returns a client with its own connection settings. Passing it through the client option of fetch routes only that call through the proxy; every other fetch in the process is unaffected.
const client = Deno.createHttpClient({
proxy: { url: "http://localhost:8080/" },
});
const response = await fetch("http://example.com/", { client });
const body = await response.text();
console.log("status:", response.status);
console.log("got example.com:", body.includes("Example Domain"));Close the client and stop the proxy so the script exits.
client.close();
await proxy.shutdown();The proxy logs the absolute URL it was asked for, which proves the request went through it rather than straight to example.com: deno run -N fetch_http_proxy.ts Listening on http://0.0.0.0:8080/ (http://localhost:8080/) proxy saw: GET http://example.com/ status: 200 got example.com: true
To proxy everything without touching code, set the environment variables instead. NO_PROXY lists hosts that bypass the proxy: HTTP_PROXY=http://localhost:8080 deno run -N main.ts NO_PROXY=localhost,127.0.0.1 HTTPS_PROXY=http://proxy.example.com:3128 deno run -N main.ts
Run this example locally using the Deno CLI:
deno run -N https://docs.deno.com/examples/scripts/fetch_http_proxy.ts