Looking at the rails pjax_rails gem https://github.com/rails/pjax_rails https://github.com/rails/pjax_rails I see it automatically patches layout to return fals

Looking at the rails pjax_rails gem https://github.com/rails/pjax_rails https://github.com/rails/pjax_rails I see it automatically patches layout to return false when the request is pjax. https://github.com/rails/pjax_rails/blob/master/lib/pjax.rb#L5 https://github.com/rails/pjax_rails/blob/master/lib/pjax.rb#... layout ->(c) { pjax_request? ? false : 'application' } So in the sample app you pointed out: def show @post = Post.find(params[:id]) if pjax_request? render layout: false else respond_to :html end end is the same as: def show @post = Post.find(params[:id]) end Also, pjax-rails converts the following selection to pjax: https://github.com/rails/pjax_rails/blob/master/lib/assets/javascripts/pjax/enable_pjax.js.coffee https://github.com/rails/pjax_rails/blob/master/lib/assets/j... $('a:not([data-remote]):not([data-behavior]):not([data-skip-pjax])') I was a bit baffled by the example app since it didn't appear to be doing any pjaxy stuff, but rails being opinionated, I see all links are pjax(except the not classes show above), and layout is turned off for pjax requests.