mastodon/config/initializers/mime_types.rb

# Be sure to restart your server when you modify this file.

Mime::Type.register 'application/json', :json, %w(text/x-json application/jsonrequest application/jrd+json application/activity+json application/ld+json)
Mime::Type.register 'text/xml',         :xml,  %w(application/xml application/atom+xml application/xrd+xml)