(last modified 2021-12-07)

Media type name: image

Media subtype name: png

Required parameters: None

Optional parameters: None

Encoding considerations: binary

Security considerations: A PNG document is composed of a collection 
   of explicitly typed "chunks".

   For each of the chunk types defined in the PNG specification 
   (except for "gIFx"), the only effect associated with those chunks 
   is to cause an image to be rendered on the recipient's display or 
   printer.

   The gIFx chunk type is used to encapsulate Application Extension
   data, and some use of that data might present security risks, 
   though no risks are known. Likewise, the security risks associated 
   with future chunk types cannot be evaluated, particularly 
   unregistered chunks. However, it is the intention of the PNG group 
   to disallow chunks containing "executable" data to become 
   registered chunks.

   The text chunks, tEXt and zTXt, contain data that can be displayed 
   in the form of comments, etc. Some operating systems or terminals 
   might allow the display of textual data with embedded control 
   characters to perform operations such as re-mapping of keys, 
   creation of files, etc. For this reason, the specification 
   recommends that the text chunks be filtered for control characters 
   before direct display.

   The PNG format is specifically designed to facilitate early 
   detection of file transmission errors, and makes use of cyclical 
   redundancy checks to ensure the integrity of the data contained in 
   its chunks.

Interoperability considerations: Network byte order used throughout.

Published specification: 

   Portable Network Graphics (PNG) Specification
   https://www.w3.org/TR/PNG/

Applications which use this media: PNG is widely implemented in all 
   Web browsers, image viewers, and image creation tools

Fragment identifier considerations: N/A

Restrictions on usage: N/A

Additional information:

   1. Deprecated alias names for this type: N/A
   2. Magic number(s): 89 50 4E 47 0D 0A 1A 0A
   3. File extension(s): .png
   4. Macintosh file type code: N/A
   5. Object Identifiers: N/A

General Comments: This registration updates the earlier one as follows

   1) The old one points to an expired Internet Draft. This updated 
   registration points to a W3C Recommendation.

   2) The old contact person is sadly deceased. The new contact email 
   is a publicly archived W3C mailing list for the PNG Working Group.

   3) Change controller is W3C

Person to contact for further information:

   1. Name: PNG Working Group
   2. Email:public-png&w3.org

Intended usage: Common

Author/Change controller: W3C