_utf8 POST parameter on gmail login contains a snowman character [duplicate]

Question

Possible Duplicate:
What is the _snowman param in Ruby on Rails 3 forms for?

If you inspect the POST parameters of Gmail login with Firebug or Chrome developer tools, you'll see a _utf8 parameter with a value of ☃:

_utf8:☃

(See the attached image in case your browser doesn't render the value. It's a snowman, U+2603, http://www.utf8-character.info/#!%E2%98%83.)

Why do they do this? Is it possible that they somehow test for browser compatibility to UTF-8?

Answer 1

The _utf8 header along with a Unicode character is to ensure that

1. At least one Unicode character is submitted to the server
2. Force certain non-compliant browsers to respect the form's character encoding

In some cases, the _utf8 header is given a value of a ☃ and sometimes it is a ✓. What it is doesn't really matter and may have arbitrarily been chosen for fun.