Mime Types Plus

It works out-of-the-box, used to allow SVG upload.
Extension: svg
Mime Type: image/svg+xml
File type: image

Fulfills its function I have added the .avif format and now I can upload this type of files to my website. Thanks!

The other 2 plugins named "xxx file type xxx" didn't work. But this just works out of the box! Love it.

I don't know whats wrong with those people complain about a perfect product. It works right out of the box and when something is missing you can ad it by your self ... and when you don't know why its not working, wtf there is a support button on here -> get there and ask! This is worth 5 stars as it saves me a lot of time on every WP installation. Thank you and keep up the good work! Dennis

Very simple to install and to use.

the Does not work

It takes a few minutes to get used to the usage of the plugin. It works on 5.0.3, lets me add all files I need so far and seems to be very lightweight. But: Please, make this more intuitive. Use words like "Add" or "Delete" instead of just placing a random update-button.

Sorry to say that the logic of the settings page makes no sense. Grayed areas that you can't do anything with make it difficult. Now I add my mime type of .mp4 and it doesn't even work.

After struggling to allow certain mime types on my media uploads, this was the only plugin that actually did the job! Thanx!

The UI is unclear. There are greyed-out checkboxes beside the types which are recognized by WordPress already. You can NEVER enable or disable them, so showing disabled checkboxes beside them is confusing, as it implies there's some way to enable them, but there isn't. Just LIST the built-in types, please, without implying that they can be edited. Also label them as the built-in types.
Checking a box beside something is generally considered to mean that you're enabling it. Here, checking a box means you want to delete it. Counterintuitive. Please use a red-X or minus control rather than a checkbox to mark things for deletion.
It would be VERY HELPFUL to have a built-in list of the more common unrecognized filetypes that could be enabled with one click or check, rather than having to look up the MIME type online every time. epub, mobi, and azw formats in particular.