The "data" URL scheme (RFC2397)
Original Publication Date: 1998-Aug-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
A new URL scheme, "data", is defined. It allows inclusion of small data items as "immediate" data, as if it had been included externally.
Network Working Group L. Masinter
Request for Comments: 2397 Xerox Corporation
Category: Standards Track August 1998
The "data" URL scheme
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1998). All Rights Reserved.
A new URL scheme, "data", is defined. It allows inclusion of small
data items as "immediate" data, as if it had been included
Some applications that use URLs also have a need to embed (small)
media type data directly inline. This document defines a new URL
scheme that would work like 'immediate addressing'. The URLs are of
optional parameters.) The appearance of ";base64" means that the data
is encoded as base64. Without ";base64", the data (as a sequence of
octets) is represented using ASCII encoding for octets inside the
range of safe URL characters and using the standard %xx hex encoding
of URLs for octets outside that range. If
defaults to text/plain;charset=US-ASCII. As a shorthand,
"text/plain" can be omitted but the charset parameter supplied.
The "data:" URL scheme is only useful for short values. Note that
some applications that use URLs may impose a length limit; for
example, URLs embedded within anchors in HTML have a length limit
determined by the SGML declaration for HTML [RFC1866]. The LITLEN
(1024) limits the number of characters which can appear in a single
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.
dataurl := "data:" [ mediatype ] [ ";base64" ] "," data
mediatype := [ type "/" subtype ] *( ";" parameter )
data := *urlchar
parameter := attribute "=" value
where "urlchar" is imported from [RFC2396], and "type", "subtype",
"attribute" and "value" are the corresponding tokens from [RFC2045],
represented using URL escaped encoding of [RFC2396] as necessary.
Attribute values in [RFC2045] 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 ...