GM.xmlHttpRequest

Description

This method performs a similar function to the standard XMLHttpRequest object, but allows these requests to cross the same origin policy boundaries.

Compatibility: Greasemonkey 0.2.5+

Syntax

function GM_xmlhttpRequest( details )

Arguments

This method only takes one argument, the details object. Described below are the properties that may be defined on that object. See #Examples for more detail on how to use each.

method

String Type of HTTP request to make (E.G. "GET", "POST")

url

String The URL to make the request to. Must be an absolute URL, beginning with the scheme.

headers

Object Optional. A set of headers to include in the request. ^[2]

overrideMimeType

String (Compatibility: 0.6.8+) Optional. A MIME type to specify with the request (E.G. "text/html; charset=ISO-8859-1").

data

String Optional. Data to send in the request body. Usually for POST method requests. ^[1]

binary

Boolean (Compatibility: 0.8.3+) Optional, default false. When true, use the underlying .sendAsBinary() method.

onerror

Function Optional. Will be called if an error occurs while processing the request. Passed one argument, the #Response Object.

onload

Function Optional. Will be called when the request has completed successfully. Passed one argument, the #Response Object.

onreadystatechange

Function Optional. Will be called repeatedly while the request is in progress. Passed one argument, the #Response Object.

Response Object

All three of the callback functions defined in the details object, if called, will receive this type of object as their first (and only) argument.

status

Integer The HTTP response status (E.G. 200 or 404) upon success, or null upon failure.

statusText

String The HTTP response status line (E.G. "OK", "Not Found") upon success, or null upon failure.

readyState

Number The readyState as defined in XMLHttpRequest.

responseText

String The responseText as defined in XMLHttpRequest.

responseHeaders

String The response headers as defined in XMLHttpRequest.

finalUrl

String (Compatibility: 0.8.0+) The final URL requested, if Location redirects were followed.

Returns

undefined

As of version 0.8.5, an object with one method, abort().

Examples

Bare Minimum

GM_xmlhttpRequest({
  method: "GET",
  url: "http://www.example.com/",
  onload: function(response) {
    alert(response.responseText);
  }
});

GET request

GM_xmlhttpRequest({
  method: "GET",
  url: "http://www.example.net/",
  headers: {
    "User-Agent": "Mozilla/5.0",    // If not specified, navigator.userAgent will be used.
    "Accept": "text/xml"            // If not specified, browser defaults will be used.
  },
  onload: function(response) {
    // Inject responseXML into existing Object if not present
    if (!response.responseXML) {
      response.responseXML = new DOMParser()
        .parseFromString(response.responseText, "text/xml");
    }

    GM_log([
      response.status,
      response.statusText,
      response.readyState,
      response.responseHeaders,
      response.responseText,
      response.finalUrl,
      response.responseXML
    ].join("\n"));
  }
});

POST request

When making a POST request, most sites require the Content-Type header to be defined as such:

GM_xmlhttpRequest({
  method: "POST",
  url: "http://www.example.net/login",
  data: "username=johndoe&password=xyz123",
  headers: {
    "Content-Type": "application/x-www-form-urlencoded"
  },
  onload: function(response) {
    if (response.responseText.indexOf("Logged in as") > -1) {
      location.href = "http://www.example.net/dashboard";
    }
  }
});

HEAD request

As defined in HTTP, you may issue a HEAD request to get the response headers, without receiving the entire response body.

GM_xmlhttpRequest({
  url: "http://www.example.com",
  method: "HEAD",
  onload: function(response) {
    GM_log(response.responseHeaders);
  }
});

Notes

¹ Note that if the data field contains form-encoded data, you usually must also set the header 'Content-Type': 'application/x-www-form-urlencoded' in the headers field.

² Some headers may not actually work through GM_xmlhttpRequest. For example, the Referer header cannot be overriden. [1] [2]