Many websites either recommend or force you to disable ad-blocking software such as Adblock Plus. This script overrides that restriction in some cases and allows your ad blocker to function as expected. This can be godsend on bloated, crappy, and/or intrusive pages.It's not perfect, but it's better than nothing. Firefox Greasemonkey, especially, can run on a page which has JS blocked. The page can see, use, change, or block the script. It's nowhere near as easy as also runs the external JS from a local copy - speeding execution and all but eliminating reliance on an external server. Using external libraries introduces even more conflicts and timing issues. Tampermonkey supports GM_ functions almost fully, however.Ĭan cause side effects or conflicts with the page's JS. Note that currently Chrome only supports GM_addStyle, GM_xmlhttpRequest, GM_log and GM_openInTab, fully, natively. The script, at least the injected parts, cannot use the enhanced privileges (especially cross-domain) provided by the GM_ functions - especially GM_xmlhttpRequest(). Often easier to debug the whole script developer tools work normally.Almost always fully compatible between Chrome, Firefox, Opera, etc.The only way for non-Tampermonkey userscripts to access objects or functions provided by the target page.This bypasses the sandbox and is the only way on a normal Chrome userscript for a script to interact with the page's JS. ), you are injecting code into the target page. When you do that 'trick' ( var script = document.createElement('script'). It might work using the Tampermonkey extension on Chrome, but I'm not going to double-check that right now. That said, the version of your script that used unsafeWindow should work on/in Firefox if implemented correctly. It is the same as window in the script scope (which is not window in the page scope). Recent versions of Chrome now provide an object named unsafeWindow, for very-limited compatibility, but this object does not provide any access to the target page's JS. Strictly blocks any access to the page's JS by the script and vice-versa.Wraps the script in an anonymous function.But beware that it is possible for hostile webmasters to follow unsafeWindow usage back to the script's context and thus gain elevated privileges to pwn you with. Provides unsafeWindow to access the target page's javascript.Wraps the script in an anonymous function by default.Runs scripts in an XPCNativeWrapper sandbox, unless none is in effect (as of GM 1.0).However, the methods are different for each browser. This is done to help keep you from being hacked, but it also reduces conflicts and unexpected side-effects. Both Chrome userscripts/content-scripts and Greasemonkey scripts are isolated from the page's javascript. See 'Are Chrome user-scripts separated from the global namespace like Greasemonkey scripts?'.

Tampermonkey is safe