How do I allow Cross-Origin Requests from greasemonkey scripts in Firefox?
cross-domain, firefox, google-chrome, javascript, localhost
Solution
Normally `XMLHttpRquest`, and that includes jQuery's higher-level API around it, does not allow unrestricted cross-site requests but is limited by the same-origin policy and CORS.
As @epascarello already pointed out, you may use `GM.xmlHttpRequest` which allows you to perform any cross-site XHR even when the server does not implement CORS or allows the origin site. It also comes with some other goodies.
You should add a `@grant GM.xmlHttpRequest` metadata block to your user script or your script may break in the future.
Since you mentioned Chrome extensions: Firefox extensions can perform cross-site XHR as well. e.g. most user scripts should be easily portable to an SDK add-on using `PageMod` and enabling certain permissions analog to what you'd do in a Chrome extension.
Problem
I'm developing a Greasemonkey script that implements a couple of tools onto a webpage. This script makes a request for data from ``` http://localhost/chess/heartbeat.php ``` Now currently in Firefox I am getting this console error which totally stops my jQuery AJAX request for data. Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at ``` http://localhost/chess/heartbeat.php. ``` This can be fixed by moving the resource to the same domain or enabling CORS. I am able to work around this using Google Chrome. When I have it as a simple browser extension for chrome, I'm able to have it do the same thing as Greasemonkey and I can add the following permissions to the manifest file for the plugin which allows me to make the same data request which Firefox blocked: ``` "permissions": [ "<all_urls>" ] ``` Anyway, this works on chrome, but I want to achieve the same effect on Firefox. I've been researching this issue and I can't find a simple answer.