Is there a bullet proof way to detect MIME type of uploaded file in Ruby or Ruby on Rails? I'm uploading JPEGs and PNGs using SWFupload and
The ruby-filemagic gem will do it:
require 'filemagic' puts FileMagic.new(FileMagic::MAGIC_MIME).file(__FILE__) # => text/x-ruby; charset=us-ascii
This gem does not look at the file extension at all. It reads a bit of the file contents and uses that to guess the file's type.