(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