facebook open graph crawler triggering json response in rails actions

Question

For some reason the facebook crawler is triggering the json response in my rails actions. This causes the action to just return a json representation of the object, without

Answer 1

Check what HTTP request headers the Facebook crawler is sending – especially the Accept header.

Could well be that they send a value that let’s your application think it has to send something different then the normal HTML output.

Answer 2

Ok so Facebook sends an accepts header of

*/*

Since no specific format is requested, rails just goes down the respond_to block in order. If you list your js first in the respond_to block like below rails will respond to the facebook open crawler with JSON which will not work:

respond_to do |format|
  format.js { render :json => @this.to_json }
  format.html
end

Just switch the order so by default rails responds with HTML:

respond_to do |format|
  format.html
  format.js { render :json => @this.to_json }
end

I'm not sure why Facebook does not specify the format they are looking for... seems pretty idiotic to me. Hopefully this is helpful to somebody down the road.