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What is P2P Download?

P2P (Peer-to-Peer) downloads capture files directly in the browser memory without ever uploading them to cloud storage. When a user downloads a file in your browser session, instead of the file going to Anchor’s servers, it’s intercepted and made available to you immediately through browser hooks.

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How It Works

Traditional downloads follow this path:

  • User clicks download → File goes to browser → File uploads to Anchor’s servers → You fetch from Anchor’s servers

P2P downloads work differently:

  • User clicks download → File captured in browser memory → You fetch from the browser

The browser intercept download events, allowing you to extract the file data directly without any cloud storage involved.

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Implementation Example

import { promises as fs, existsSync } from "node:fs";
import { chromium } from "playwright";

const { ANCHOR_API_KEY } = process.env;

/**
 * Save a download to disk.
 * Handles three possible formats:
 *   1. Playwright Download object
 *   2. Base‑64 string
 *   3. Fallback text scraped from the page
 */
async function saveDownload(download, filePath, page) {
  // 1. Playwright Download object
  if (download && typeof download.path === "function") {
    try {
      const tmpPath = await download.path();
      if (tmpPath && existsSync(tmpPath)) {
        await download.saveAs(filePath);
        return filePath;
      }
    } catch {
      /* ignore and fall through */
    }
  }

  // 2. Raw base64 string
  if (typeof download === "string") {
    try {
      await fs.writeFile(filePath, Buffer.from(download, "base64"));
      return filePath;
    } catch {
      /* ignore and fall through */
    }
  }

  // 3. Fallback – ask the page for data or capture visible text
  if (page) {
    try {
      const blob = await page.evaluate(() => window._anchorExtractDownloadData());
      return saveDownload(blob, filePath);
    } catch {
      /* ignore and fall through */
    }

    const fallbackText = await page.evaluate(() => {
      const el = document.querySelector("main") || document.body;
      return el.innerText || "";
    });
    await fs.writeFile(filePath, fallbackText, "utf8");
    return filePath;
  }
  throw new Error("Failed to save download");
}

const downloadHandler = (filePath) => async (page, info) => {
  if (info?.value) {
    try {
      return await saveDownload(info.value, filePath);
    } catch {
      /* ignore and fall through */
    }
  }
  return saveDownload(null, filePath, page);
};

async function createSession() {
  const res = await fetch("https://api.anchorbrowser.io/v1/sessions", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "anchor-api-key": ANCHOR_API_KEY,
    },
    body: JSON.stringify({ browser: { p2p_download: { active: true } } }),
  });
  if (!res.ok) throw new Error(`Anchor API error ${res.status}: ${await res.text()}`);
  const { data } = await res.json();
  return data;
}

(async () => {
  const session = await createSession();
  if (!session?.cdp_url) throw new Error("No CDP URL in session");

  const browser = await chromium.connectOverCDP(session.cdp_url);
  const context = browser.contexts()[0];
  const page = context.pages()[0];

  await page.goto("https://v0-download-and-upload-text.vercel.app/");
  await page.waitForSelector("button");

  const [download] = await Promise.all([
    page.waitForEvent("download", { timeout: 5000 }),
    page.click("button"),
    page.waitForTimeout(500), // allow JS to finish
  ]);

  const filename = download.suggestedFilename();
  await downloadHandler(filename)(page, { value: download });

  const content = await fs.readFile(filename, "utf8");
  console.log(`Downloaded '${filename}', content:\n${content}`);

  await browser.close();
})();