Heroku is readonly file system hence write operations can only be done inside tmp directory.
Asset compilation on heroku can be handled in different ways
#1. compiling locally and placing inside assets directory RAILS_ENV=production bundle exec rake assets:precompile #2. It compiles assets while slug compiles
#3. Run time asset compilation # It compiles assets for every rails request if it notifies assets got modified # config/application.rb # Enable the asset pipeline config.assets.enabled = true # Version of your assets, change this if you want to expire all your assets config.assets.version = '1.0' config.assets.prefix = Rails.root.join('tmp/assets').to_s # config/environments/production.rb # Don't fallback to assets pipeline if a precompiled asset is missed config.assets.compile = true
Note: write operation made inside tmp directory can not make any guarantee of being persisted hence be careful while using.