Can I modify outgoing request headers with a Chrome Extension?

Question

I can't see an answer to this in the Developer's Guide, though maybe I'm not looking in the right place.

I want to intercept HTTP requests with a Chrome Extension, and then forward it on, potentially with new/different HTTP headers - how can I do that?

Answer 1

PS: I am the author of this extension so you can blame me for anything you don't like :)

It was certainly not possible when OP asked the question but soon later Chrome released experimental WebRequest API. But now they have been included officially in Chrome Extension. You can use it modify request and response headers in Chrome.

Look at this example:

chrome.webRequest.onBeforeSendHeaders.addListener(
  function(details) {
    for (var i = 0; i < details.requestHeaders.length; ++i) {
      if (details.requestHeaders[i].name === 'User-Agent') {
        details.requestHeaders.splice(i, 1);
        break;
      }
    }
    return { requestHeaders: details.requestHeaders };
  },
  {urls: ['<all_urls>']},
  ['blocking', 'requestHeaders' /* , 'extraHeaders' */]
  // uncomment 'extraHeaders' above in case of special headers since Chrome 72
  // see https://developer.chrome.com/extensions/webRequest#life_cycle_footnote
);

If you want to use Chrome Extension, you can use Requestly which allows you to modify request and response headers as you wish. Have a look at this snapshot: