Rails forms automatically insert a hidden utf8 field? (a.k.a. what’s with the checkmark/snowman?)

Yes, apparently this is true according to a response on StackOverflow. Let’s say you have a simple form from a model:

  <%= form_for @some_model do |f| %>
  <% end %>

You might see the following output in the generated HTML:

  <div style="margin:0;padding:0;display:inline">
  <input name="utf8" type="hidden" value="&#x2713;" />
  ...other stuff...

Apparently in order to force browsers to submit the form in UTF-8 encoding mode this UTF-8 value (✓) does the trick. If you peer into the code you can see inside the actionpack form_tag_helper.rb that this is called the “snowman_tag”. A little Googling reveals this post on http://railssnowman.info:

What’s with the _utf8/_e/_snowman tag in Rails 3?

The _utf8 input tag forces Internet Explorer to properly respect your form’s character encoding.

Rails uses the accept-charset attribute in your form element to let the server know that it should be able to deal with unicode characters (think of a user searching for café).

But it looks like old snowman value &#9731; (☃) has been since replaced with the simple check mark &#x2713; (✓). 🙂

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