RFC 2397 (rfc2397) - Page 2 of 5

The "data" URL scheme

RFC 2397                 The "data" URL scheme               August 1998


   attribute value literal, the ATTSPLEN (2100) limits the sum of all
   lengths of all attribute value specifications which appear in a tag,
   and the TAGLEN (2100) limits the overall length of a tag.

   The "data" URL scheme has no relative URL forms.

3. Syntax

       dataurl    := "data:" [ mediatype ] [ ";base64" ] "," data
       mediatype  := [ type "/" subtype ] *( ";" parameter )
       data       := *urlchar
       parameter  := attribute "=" value

   where "urlchar" is imported from [RFC 2396], and "type", "subtype",
   "attribute" and "value" are the corresponding tokens from [RFC 2045],
   represented using URL escaped encoding of [RFC 2396] as necessary.

   Attribute values in [RFC 2045] are allowed to be either represented as
   tokens or as quoted strings. However, within a "data" URL, the
   "quoted-string" representation would be awkward, since the quote mark
   is itself not a valid urlchar. For this reason, parameter values
   should use the URL Escaped encoding instead of quoted string if the
   parameter values contain any "tspecial".

   The ";base64" extension is distinguishable from a content-type
   parameter by the fact that it doesn't have a following "=" sign.

4. Examples

   A data URL might be used for arbitrary types of data. The URL

                          data:,A%20brief%20note

   encodes the text/plain string "A brief note", which might be useful
   in a footnote link.

   The HTML fragment:

   




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