Accessing raw post data with raw_post in Rails

How to Access Raw POST Data in Rails

This post shows how you can access the raw, unaltered request body using a 20-year old method in the Rails framework (from the founder of Shopify). The `raw_post` method reads the request body, and is useful for web services or API controllers that need to directly work with raw requests.

1 min read
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If you are building an API or any sort of web services, you often want to work with the raw, unchanged request body. For a long time, I used to add this helper method in my Rails controllers to access the the incoming request body.

def request_body
  @request_body ||= (

Recently, in one of the code reviews at work, I came across the raw_post method in Rails which does this for you. Here's what the method is doing behind the scenes.

# actionpack/lib/action_dispatch/http/request.rb

def raw_post
  unless has_header? "RAW_POST_DATA"
    set_header("RAW_POST_DATA", read_body_stream)
    body_stream.rewind if body_stream.respond_to?(:rewind)
  get_header "RAW_POST_DATA"

def read_body_stream
  body_stream.rewind if body_stream.respond_to?(:rewind)
  return if headers.key?("Transfer-Encoding") # Read body stream until EOF if "Transfer-Encoding" is present

In your Rails controller, you can access this method as follows:


I am surprised I never ran into this method before, as it has existed in Rails for over two decades, and was introduced by none other than Tobias Lütke, the founder of Shopify! Quite a piece of open source history, isn't it?

That's a wrap. I hope you found this article helpful and you learned something new.

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