February 2, 1996
Expires in 6 months

                       "Data: URL scheme"

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A new URL scheme, "data:", is defined. It allows inclusion of small
data items as "immediate" data, as if it had been included externally.


Some applications that use URLs also have a need to embed (small)
media type data directly inline. This proposal includes a new
URL scheme that would work like 'immediate addressing'. The format
of the URL is as follows:


where <mediatime> is a media type (with optional parameters, etc.).
The token "base64" means that the value is encoded as base64.
Otherwise, the value is encoded with the standard %xx URL encoding.

The mediatype, if left blank, defaults to text/plain;charset=US-ASCII.
As a shorthand, "text/plain" can be omitted but the charset parameter


This is only to be used for very short data types. For example,


encodes the string "A brief note"

might be useful in a footnote link, while,


could be used for a small inline image in a HTML document.

This is only appropriate for delivery of very small inline data. The
embedded image above is probably near the limit of utility. For
anything else larger, or where the base64 encoding is problematic or
cumbersome, immediate data references within URLs are inappropriate.


This idea was originally proposed August 1995 by the author, and
recently revised because of the appearance of a (weaker) proposal in
a HTML INSERT proposal. This version allows eliding the media type,
packs the indication of the base64 encoding more tightly, and
eliminates the proposal to allow quoted printable, since the encoding
would not easily yield valid URLs without additional %xx encoding,
which itself is sufficient.


Immediate data URLs introduce no new security considerations.

Author contact information:

Larry Masinter
Xerox Palo Alto Research Center
3333 Coyote Hill Road
Palo Alto, CA 94304