Verbose paperclip file extensions Basic: csv, pdf, txt | Microsoft: doc, docx, ppt, pptx, xls, xlsx | Images: gif, jpg, jpeg, png | Apple: pages, numbers

paper_clip_extensions.rb

# If you want to add to your list, you can sniff using a binding.pry
# Look at the ActionDispatch::Http::UploadedFile object's Content-Type in the @header variable

validates_attachment :attachment,
                     allow_blank: false,
                     content_type: { content_type: ['image/jpg', #image
                                                    'image/jpeg', #image
                                                    'image/gif', #image
                                                    'image/png', #image
                                                    'application/pdf', #pdf
                                                    'application/msword', #word doc
                                                    'applicationvnd.ms-word', #word doc
                                                    'application/vnd.openxmlformats-officedocument.wordprocessingml.document', #word docx
                                                    'application/msexcel', #excel xls
                                                    'application/vnd.ms-excel', #excel xls
                                                    'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', #excel xlsx
                                                    'application/mspowerpoint', #powerpoint ppt
                                                    'application/vnd.ms-powerpoint', #powerpoint ppt
                                                    'application/vnd.openxmlformats-officedocument.presentationml.presentation', #powerpoint pptx
                                                    'application/x-iwork-pages-sffpages', #apple's pages
                                                    'application/x-iwork-keynote-sffnumbers', #apple's numbers
                                                    'text/plain', #txt
                                                    'text/csv'] }, # csv
                     file_name: { matches: [/csv\z/,
                                            /docx?\z/,
                                            /gif\z/,
                                            /jpe?g\z/,
                                            /numbers\z/,
                                            /pages\z/,
                                            /pdf\z/,
                                            /png\z/,
                                            /pptx?\z/,
                                            /txt\z/,
                                            /xlsx?\z/] }