Puppeteer with an authenticated proxy — page.authenticate, and why the launch flag alone fails https://quanticdata.io/blog/how-to-use-a-proxy-in-puppeteer/

qd-puppeteer-proxy.mjs

/**
 * Puppeteer through an authenticated proxy.
 *
 * The trap: --proxy-server takes a host and port, and NOTHING ELSE. Credentials in
 * the URL are ignored by Chrome, and you get a 407 with no obvious explanation.
 * The username and password go through page.authenticate() instead — per page,
 * before the first navigation.
 *
 *   npm i puppeteer
 *   QD_PROXY_USER=... QD_PROXY_PASS=... node qd-puppeteer-proxy.mjs
 *
 * https://quanticdata.io/residential-proxies/
 * Guide: https://quanticdata.io/blog/how-to-use-a-proxy-in-puppeteer/
 */
import puppeteer from "puppeteer";

const GATEWAY = "pr.quanticdata.io:7777";
const USER = process.env.QD_PROXY_USER;
const PASS = process.env.QD_PROXY_PASS;

// Chrome takes one proxy per browser process, so the country is fixed at launch.
// Need several countries at once? Launch several browsers, or use Playwright,
// which sets the proxy per CONTEXT — see
// https://github.com/quantumproxies/quanticdata-proxy-quickstart
const COUNTRY = process.argv[2] || "us";
const SESSION = process.argv[3] || null;

const browser = await puppeteer.launch({
  headless: "new",
  args: [`--proxy-server=${GATEWAY}`, "--no-sandbox"],
});

const page = await browser.newPage();

// Targeting lives in the username; the session suffix pins one exit IP.
const username = [USER, "country", COUNTRY, ...(SESSION ? ["session", SESSION, "sessTime", "10"] : [])].join("-");
await page.authenticate({ username, password: PASS });

await page.goto("https://ipinfo.io/json", { waitUntil: "domcontentloaded" });
const body = await page.evaluate(() => document.body.innerText);
console.log(`country=${COUNTRY}${SESSION ? ` session=${SESSION}` : " (rotating)"}`);
console.log(body.trim());

await browser.close();