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Internet Engineering Task Force (IETF)                         J. LevineRequest for Comments: 6713                          Taughannock NetworksCategory: Informational                                      August 2012ISSN: 2070-1721The 'application/zlib' and 'application/gzip' Media TypesAbstract   This document defines the 'application/gzip' and 'application/zlib'   media types for compressed data using the gzip and zlib compression   formats.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6713.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Levine                        Informational                     [Page 1]

RFC 6713              Media Types 'zlib' and 'gzip'          August 20121.  Introduction   zlib [RFC1950] and gzip [RFC1952] are widely used compression   formats. zlib is a stream format, while gzip adds header and trailer   fields more appropriate for a file format.  Both implement the   DEFLATE compression scheme described in [RFC1951].   They are used to compress a wide variety of material, from   unstructured text to structured data to executable code.   Some applications have informally used media types such as   application/gzip-compressed, application/gzipped, application/   x-gunzip, application/x-gzip, application/x-gzip-compressed, and   gzip/document to describe data compressed with gzip.  The media types   defined in this document should replace those media types in future   applications.2.  The 'application/zlib' Media Type   The 'application/zlib' media type describes a block of data that is   compressed using zlib [RFC1950] compression.  The data is a stream of   bytes as described inRFC 1950.2.1.  Registration Details   Type name: application   Subtype name: zlib   Required parameters: N/A   Optional parameters: N/A   Encoding considerations: Binary   Security considerations: SeeSection 4 below.   Interoperability considerations: N/A   Published specification: [RFC1950]   Applications that use this media type: anywhere data size is an issue   Additional information:      Magic number(s): first byte is usually 0x78 but can also be 0x08,      0x18, 0x28, 0x38, 0x48, 0x58, or 0x68.  The first two bytes, when      interpreted as an unsigned 16-bit number in big-endian byte order,      contain a value that is a multiple of 31.Levine                        Informational                     [Page 2]

RFC 6713              Media Types 'zlib' and 'gzip'          August 2012      File extension(s): N/A      Macintosh file type code(s): N/A   Person and email address to contact for further information: seehttp://www.zlib.net/   Intended usage: COMMON   Restrictions on usage: N/A   Author: John Levine   Change controller: IETF3.  The 'application/gzip' Media Type   The 'application/gzip' media type describes a block of data that is   compressed using gzip [RFC1952] compression.  The data is a stream of   bytes as described inRFC 1952.3.1.  Registration Details   Type name: application   Subtype name: gzip   Required parameters: N/A   Optional parameters: N/A   Encoding considerations: Binary   Security considerations: SeeSection 4 below.   Interoperability considerations: N/A   Published specification: [RFC1952]   Applications that use this media type: anywhere data size is an issue   Additional information:      Magic number(s): first two bytes are 0x1f, 0x8b.      File extension(s): gz      Macintosh file type code(s): N/A   Person and email address to contact for further information: seehttp://www.gzip.org/Levine                        Informational                     [Page 3]

RFC 6713              Media Types 'zlib' and 'gzip'          August 2012   Intended usage: COMMON   Restrictions on usage: N/A   Author: John Levine   Change controller: IETF4.  Security Considerations   zlib and gzip compression can be used to compress arbitrary binary   data such as hostile executable code.  Also, data that purports to be   in zlib or gzip format may not be, and fields that are supposed to be   flags, lengths, or pointers could contain anything.  Applications   should treat any data with due skepticism.   Also see the security considerations in the underlying format   documents:Section 5 of [RFC1950],Section 6 of [RFC1951], andSection 4 of [RFC1952].5.  IANA Considerations   IANA has updated the "Application Media Types" registry to include   'application/zlib' as described inSection 2 and 'application/gzip'   as described inSection 3.6.  Normative References   [RFC1950]  Deutsch, P. and J-L. Gailly, "ZLIB Compressed Data Format              Specification version 3.3",RFC 1950, May 1996.   [RFC1951]  Deutsch, P., "DEFLATE Compressed Data Format Specification              version 1.3",RFC 1951, May 1996.   [RFC1952]  Deutsch, P., "GZIP file format specification version 4.3",RFC 1952, May 1996.Author's Address   John Levine   Taughannock Networks   PO Box 727   Trumansburg, NY  14886   Phone: +1 831 480 2300   EMail: standards@taugh.comLevine                        Informational                     [Page 4]