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According to RFC 3987, URLs must be converted to UTF-8 character encoding. IE and Opera, contrary to the specification, encode the path part of the URL in UTF-8 but encode the query string part of the URL in the encoding of the referring page. Many servers expect IE and Opera's behaviour and break when presented with fully encoded URLs. This preference controls whether to encode URLs in UTF-8.

Possible values and their effects


Encode URLs in UTF-8 as per the standard.


Do not encode URLs at all. This is different than IE and Opera's behaviour in that not even the path is encoded. (Default)


  • Setting this preference to true can cause incompatibilities in some websites.

First checked in

2004 03-26 by Jungshik Shin

Has an effect in

  • Netscape (all versions since 7.1)
  • Mozilla Suite (all versions since 1.7RC1)
  • Firefox (all versions since 0.9)
  • Seamonkey (all versions)

Related bugs

Related preferences