IE and MIME-types

I’m using Paperclip for a site where a visitor can upload an image. The supported image types are gif, jpg and png.

So I created this Paperclip model validation:

validates_attachment_content_type :image, :content_type => [ 'image/jpeg', 'image/png', 'image/gif' ]

But of course something had to not work in Internet Explorer. Not obvious how a browser can affect something to fail on the server side. It turns out that IE translates the MIME-types a bit different than what other browsers do.

FORMAT          MIME-IE          MIME-OTHER
png             image/x-png      image/png
jpeg            image/pjpeg      image/jpeg

So the “correct” Paperclip validation for gif, jpg and png images would then be:

validates_attachment_content_type :image, :content_type => [ 'image/jpeg', 'image/png', 'image/gif', 'image/x-png', 'image/pjpeg' ]