Trying to add certain allowed MIME types to the upload filter - currently my custom function looks like this:

// allow SVG and video mime types for upload
function cc_mime_types( $mimes ){
    $mimes['svg']  = 'image/svg+xml';
    $mimes['webm'] = 'video/webm';
    $mimes['mp4']  = ['video/mp4','video/mpeg'];
    $mimes['ogg']  = 'video/ogg';
    $mimes['ogv']  = 'video/ogg';
    return $mimes;
add_filter( 'upload_mimes', 'cc_mime_types' );

Uploading videos with ogg/ogv format seems to work well, but MP4 is failing. It seems like an array of different MIME types is not the solution. How should I add this?


This filter only accepts strings for mime types. It also already has support for webm, mp4, mpeg, ogv, and ogg.

I think you can remove everything except the line for SVGs.

A word of warning, WordPress doesn't support SVG upload by default because it's a security concern. Be careful about enabling this. At the least, use something like the Safe SVG plugin to help mitigate the risk.

  • Not all files/extensions in this list are allowed within the upload_mime's filter (at least not in the installation I have tested it). Anyway thank you very much for the list (+1), now I know ho to do it. – Blackbam May 29 '19 at 16:11

@MikeNGarret's answer pointed me to the interesting function wp_get_mime_types(). Within this function you can look up how to correctly add MIME types to the upload_mimes filter (https://core.trac.wordpress.org/browser/tags/5.1.1/src/wp-includes/functions.php#L2707).

The correct answer therefore is:

// allow SVG and video mime types for upload
function cc_mime_types( $mimes ){
    $mimes['svg']      = 'image/svg+xml';
    $mimes['webm']     = 'video/webm';
    $mimes['mp4|m4v']  = 'video/mp4';
    $mimes['mpeg|mpg|mpe']  = 'video/mpeg';
    $mimes['ogv']      = 'video/ogg';
    return $mimes;
add_filter( 'upload_mimes', 'cc_mime_types' );

For registering an unknown MIME type you should therefore use the mime_types filter, for the upload (independently) you have to add it to the list of allowed upload mimes.

  • Note that this answers half the question - you can add multiple extensions to a single mime-type. But how can you do the other half, add multiple mime-types to a single extension? eg a .DXF file can legitimately be text/plain or applications/octet-stream as both text and binary versions exist. – benz001 Apr 30 '20 at 9:17
  • @benz001 Never have needed this. Have you tried an array? – Blackbam Apr 30 '20 at 11:18
  • 1
    Yes, it didn't work, also tried comma-separated mimes as per some other article - what I had to do was wrap around the check and if it failed loop through an array of alternate mime types retrying the check each time as per wordpress.stackexchange.com/questions/323750/… This seems like a core bug that there is no filter/mechanism to support this - for us it killed our file upload gravity form. – benz001 May 2 '20 at 9:11
  • @benz001 Ok thats good to know. You should do a feature request in: core.trac.wordpress.org - because this is really something WordPress should be capable of. – Blackbam May 4 '20 at 8:16

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