2.2.48 [HTML] Section 17.13.1, Form submission method
The specification states:
Note. The "get" method restricts form data set values to ASCII characters.
All Document Modes (All Versions)
When submitting form data with the get method, non-ASCII characters are percent-encoded from 8-bit Unicode Transformation Format (UTF-8) octets. For example, the character LATIN CAPITAL LETTER A WITH GRAVE would be represented as