(registered 2022-11-21, last updated 2022-11-21)

Media type name: image

Media subtype name: apng

Required parameters: N/A

Optional parameters: N/A

Encoding considerations: binary

Security considerations: An APNG 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 animated image to be 
   rendered on the recipient's display.

   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 
   Working Group to disallow chunks containing "executable" data to 
   become registered chunks.

   The text chunks, tEXt, iTXt 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.

   If one creates an APNG file with unrelated static image and 
   animated image chunks, somebody using a tool not supporting the 
   APNG format would only see the static image and be unaware of
   the additional content. This could be used e.g. to bypass 
   moderation. 

Interoperability considerations: None

Published specification: Portable Network Graphics (PNG) 
   Specification, https://www.w3.org/TR/png/

Applications which use this media: Animated PNG (APNG) is widely 
   implemented in all Web browsers, and is increasingly available in 
   image viewers, and animation and image creation tools

Fragment identifier considerations: N/A

Restrictions on usage: N/A

Additional information:

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

General Comments: image/apng has been in widespread, unregistered use 
   since 2015. Animated PNG was not part of the official PNG 
   specification until 2022. This registration, plus the PNG 
   specification (3rd Edition) brings official documentation into 
   alignment with already widely-deployed reality.

Person to contact for further information:

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

Intended usage: COMMON

Author/Change controller: W3C