Chrome extensions - Other ways to read response bodies than chrome.devtools.network?

Question

I'd like to read (not modify) the response body for all requests that match some pattern in a Chrome extension. I'm currently using chrome.devtools.network.onRequestFinished, which gives you a Request object with a getContent() method. This works just fine, but of course requires the devtools to be open for the extension to work. Ideally the extension would be a popup, but chrome.webRequest.onCompleted doesn't seem to give access to the response body. There is a feature request to allow the webRequest API to edit response bodies - but can webRequest even read them? If not, is there any other way to read response bodies outside of devtools extensions?

Answer 1

The feature request you linked to implies that there is no support for reading either:

Unfortunately, this request is not trivial. (...) Regarding reading the Response Body: This is challenging from a performance perspective. (...) So overall, this is just not easy to achieve...

So, no, there doesn't seem to be a way for an extension to access network response bodies, except for devtools.

Answer 2

Here is what I did

1. I used the chrome.webRequest & requestBody to get the post requests body
2. I used a decoder the parse the body into a string

Here is an example

chrome.webRequest.onBeforeRequest.addListener(
    function(details) {
        if(details.method == "POST")
        // Use this to decode the body of your post
            var postedString = decodeURIComponent(String.fromCharCode.apply(null,
                                      new Uint8Array(details.requestBody.raw[0].bytes)));
           console.log(postedString)

    },
    {urls: ["<all_urls>"]},
    ["blocking", "requestBody"]
);

Answer 3

If you have the this pattern of requests you can run something like that in your background.html file:

    var xhr = new XMLHttpRequest();
    xhr.open("GET", "http://example.com/" + yourStringForPattern, true);
    xhr.onreadystatechange = function() {
    if (xhr.readyState == 4) {
      var body = xhr.responseText;
      // call some function to do something with the html body

    }
   }
   xhr.send();