URL Encoding

All HTTP messages, with the possible exception of the content section of the message, use the ISO-8859-1 (ISO-Latin) character set. An HTTP request may include an Accept-Encoding request header that identifies alternative character encodings that are acceptable for the content in the HTTP response.

URLs pose a special challenge, because their syntax does not allow the following groups of characters from the ISO-Latin character set:

  • Non-ASCII characters— The ASCII characters are a subset of the entire ISO-Latin character set, consisting of the bottom half (characters 0-127) of the entire 256 characters. All non-ASCII characters (128-255) are invalid for use in URLs.

  • Non-printable ASCII characters (control characters)— Several ASCII ...

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