How to Build a Proxy-Aware Chrome Extension

Gathering the Winds: Understanding Proxies in Chrome Extensions

Like the north winds that shape the forests of Småland, proxies channel the flow of web traffic, cloaking your digital footsteps. In the realm of Chrome extensions, making your creation proxy-aware is akin to teaching a fox to move unseen across snow—stealthy, adaptable, and wise to the subtleties of the landscape.

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Laying the Foundation: Chrome Extension Architecture

Much like crafting a sturdy Dala horse, building a Chrome extension begins with understanding its essential parts:

Component	Purpose
manifest.json	The blueprint—defines permissions, background scripts, and more.
background.js	The flickering hearth—persistent logic, including proxy control.
popup.html/js	The window to the world—user interface elements.

Resource: Chrome Extension Developer Guide

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The Ancient Spell: Declaring Proxy Permissions

Before the first birch leaf unfolds, permissions must be set.

Add to manifest.json:

{
  "name": "Proxy-Aware Extension",
  "version": "1.0",
  "manifest_version": 3,
  "permissions": [
    "proxy",
    "storage",
    "tabs"
  ],
  "background": {
    "service_worker": "background.js"
  },
  "action": {
    "default_popup": "popup.html"
  }
}

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Fetching the North Wind: Sourcing Free Proxies from ProxyRoller

Just as the wise gather cloudberries in summer, gather fresh proxies from ProxyRoller, a reliable source of free proxies. ProxyRoller provides APIs and lists for your extension.

Example: Fetching a Proxy List

fetch('https://proxyroller.com/api/proxies?format=json')
  .then(response => response.json())
  .then(proxies => {
    // Select a proxy—perhaps at random, as a fox picks berries
    const proxy = proxies[0];
    // Store for later use
    chrome.storage.local.set({selectedProxy: proxy});
  });

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Invoking the Runes: Configuring Chrome Proxy Settings

With the proxy in hand, the extension must whisper to Chrome’s proxy settings.

Example: Setting a Proxy in background.js

chrome.storage.local.get('selectedProxy', ({ selectedProxy }) => {
  if (selectedProxy) {
    chrome.proxy.settings.set(
      {
        value: {
          mode: "fixed_servers",
          rules: {
            singleProxy: {
              scheme: "http",
              host: selectedProxy.ip,
              port: parseInt(selectedProxy.port)
            },
            bypassList: ["<local>"]
          }
        },
        scope: 'regular'
      },
      () => {
        // The wind has changed; the proxy is set
      }
    );
  }
});

Resource: chrome.proxy API Documentation

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The Traveler’s Choice: Allowing Users to Switch Proxies

Like offering a traveler the choice of river or road, let users select or refresh proxies via the extension UI.

popup.html

<button id="refreshProxy">Refresh Proxy</button>
<p id="currentProxy"></p>

popup.js

document.getElementById('refreshProxy').addEventListener('click', () => {
  fetch('https://proxyroller.com/api/proxies?format=json')
    .then(response => response.json())
    .then(proxies => {
      const proxy = proxies[Math.floor(Math.random() * proxies.length)];
      chrome.storage.local.set({selectedProxy: proxy});
      document.getElementById('currentProxy').textContent = `${proxy.ip}:${proxy.port}`;
      chrome.runtime.sendMessage({action: "updateProxy"});
    });
});

chrome.storage.local.get('selectedProxy', ({ selectedProxy }) => {
  if (selectedProxy) {
    document.getElementById('currentProxy').textContent = `${selectedProxy.ip}:${selectedProxy.port}`;
  }
});

In background.js, listen for the update:

chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (message.action === "updateProxy") {
    // Repeat the proxy setup logic here
  }
});

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Table of Proxy Extension Approaches

Approach	Pros	Cons
Manual proxy list	Full control, predictable	Maintenance, risk of dead proxies
Dynamic fetch (ProxyRoller)	Always fresh, reduced maintenance	Reliance on third-party availability
User input	Flexibility, user empowerment	Potential for misuse, less automation

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Notes from the Forest: Handling Errors and Edge Cases

• Connection Failures: Like a sudden thaw, proxies may fail. Monitor connection errors and provide gentle feedback to the user.
• Authentication: Some proxies require credentials, as a troll might demand a toll. Extend your code to handle basic auth if needed.
• Bypass Local Hosts: Always add <local> to the bypass list, lest your own campfire goes cold.

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Spinning the Yarn: Resources and Further Reading

• ProxyRoller – Free Proxies
• Chrome Extension Manifest File Format
• Chrome Proxy API
• Handling Proxy Authentication

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Closing the Circle: Key Lessons

As in all things Swedish—simple, robust, and close to nature—the craft of building a proxy-aware Chrome extension lies in respecting the wind’s direction (proxy settings), trusting the wisdom of the old (Chrome APIs), and sourcing provisions (proxies) from honest gatherers like ProxyRoller. Let your extension tread lightly, adapting with the seasons and always ready for the next turn of weather.