WordPress has a set of restricted filetypes it will allow you to upload via the media library. Whilst this is a great security feature, there may be times where you’d like to add other files that are restricted by default, or maybe even the opposite where you’d only like to allow a few extensions to be uploaded. Fortunately, WordPress makes this dead easy with a small snippet of PHP code.

If you’d like to add or remove a specific filetype that can be uploaded to wordpress via the media library, you can insert this PHP code in your theme functions.php file:

function my_myme_types($mime_types){
	//Adjust the $mime_types, which is an associative array where the key is extension and value is mime type.
	return $mime_types;
}
add_filter('upload_mimes', 'my_myme_types', 1, 1);

Here is an example of what you can do to add and remove a new filetype (in this example, I’m adding an extension that already exists, but the concept is the same):

function my_myme_types($mime_types){
	$mime_types['avi'] = 'video/avi'; //Adding avi extension
	unset($mime_types['pdf']); //Removing the pdf extension
	return $mime_types;
}
add_filter('upload_mimes', 'my_myme_types', 1, 1);

You can also reset the allowed filetypes by creating a new array within the function and returning these values:

function my_myme_types($mime_types){
	//Creating a new array will reset the allowed filetypes
	$mime_types = array(
		'jpg|jpeg|jpe' => 'image/jpeg',
		'gif' => 'image/gif',
		'png' => 'image/png',
		'bmp' => 'image/bmp',
		'tif|tiff' => 'image/tiff'
	);
	return $mime_types;
}
add_filter('upload_mimes', 'my_myme_types', 1, 1);

If you’d like to see what filetypes are currently supported by wordpress, check out the function get_allowed_mime_types located in the wp-includes/functions.php file.