When trying to upload a file-type which is not by default supported by WordPress (my example was with WordPress 4.0 but this will work with earlier versions too), you will be presented with the following error:
Sorry, this file type is not permitted for security reasons.
This can be frustrating, especially if you know that the file you’re trying to upload contains no security threats at all. So, how do you fix this? Well, the answer is simpler than you might think. The reason why this error is presented is because WordPress maintains a listed of supported file-type, or MIME types. If the file-type does not appear in this list, it is not permitted to be uploaded in WordPress. So, all you have to do is add the “.apk” file-type – or any other filetype – to the supported MIME list and you’re good to go.
Unfortunately, WordPress doesn’t have a built-in interface to add new MIME types. Luckily, there is a great little plugin called “WP Add Mime Types” which is developed by Kimiya Kitani. In the past people used PJW MIME Config as well, but that one is no longer being actively developed.
So, log in to your WordPress Admin interface, go to Plugins followed by Add New and in the Search box, type “WP Add Mime Types”. Click on Install followed by Activate and you’re good to go. Now, to configure the Plugin to support apk file uploads, click Settings once more, followed by Mime Type Settings. Here you can add the following entry for apk file uploads, but you can adjust it to the needs for your filetype:
apk = application/vnd.android.package-archive
That’s it! Click on Save and you’re now able to upload apk files for your visitors to download!