The "data" URL scheme (RFC2397)
Original Publication Date: 1998-Aug-01
Included in the Prior Art Database: 2019-Feb-15
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. [STANDARDS-TRACK]
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 externally.
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 the form:
The <mediatype> is an Internet media type specification (with 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 <mediatype> is omitted, it 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 <A> 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
Masinter Standards Track [Page 1]
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.
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 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...