Chrome: NPAPI plugin is required for this app

I'm trying to install the Sway.fm Unified Music Media Keys extension for Chrome, but I'm receiving the following error message.

This application is not supported on this computer. Installation has been disabled. The following problems are detected: NPAPI plugin is required by this app

How can I resolve this problem in Chrome? No amount of Googling provided an answer for me; everything seems to indicate that something has to be done by the developer. This clearly isn't the case, however, as the extension has many positive reviews (many recent ones as well).

I'm using Chrome 31.0.1650.57 m on Windows 8.1.

Solution 1:

Download your extension with Chrome Extension Downloader and drag'n'drop the downloaded file to chrome://extensions page.

Solution 2:

NPAPI plugins cannot be installed in Chrome in Windows 8 metro mode http://blog.chromium.org/2012/07/npapi-plug-ins-in-windows-8-metro-mode.html but should still be able to work in desktop mode.

There is a bug that means they do not work https://code.google.com/p/chromium/issues/detail?id=162186 but this can be worked around by running Chrome in compatibility mode for Windows 7.

If you do this, beware that it may trigger other Chrome bugs causing performance to degrade to the point of being basically completely useless.

In order to do this, you locate the Chrome shortcut or executable, then go to properties / compatibility. I can confirm that making this change has allowed me to install the ADB plugin (for debugging webpages on a connected Android device) that was otherwise giving a similar error message.

I still seem to have some other problem with the setup of that, meaning that I'm still not actually seeing any inspection targets for my debugging... but it's fairly likely this is for some other reason, and that NPAPI part has been fixed by the workaround.