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APNG
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APNG
Animated Portable Network Graphics (APNG) is a file format which extends the Portable Network Graphics (PNG) specification to permit animated images that work similarly to animated GIF files, while supporting images with a higher color depth and full alpha transparency not available for GIFs. It also retains backward compatibility with non-animated PNG files.
The first frame of an APNG file is stored as a normal PNG stream, so most standard PNG decoders are able to display the first frame of an APNG file. The frame speed data and all of the subsequent frames are stored in extra chunks (as provided for by the original PNG specification). APNG competed with Multiple-image Network Graphics (MNG), a comprehensive format for bitmapped animations which was created by the same team as PNG and is obsolete. APNG's advantages over MNG are its smaller library size and its compatibility with older PNG implementations.
The APNG specification was created in 2004 by Stuart Parmenter and Vladimir Vukićević of the Mozilla Corporation to allow for storing the animations needed for interfaces such as throbbers. In May 2003, Mozilla had scrapped support for MNG animations, which provides a superset of APNG functionality, citing concerns about the large file size required for the expansive MNG decoder library (300 KB); the APNG decoder, built on the back of the PNG decoder, was a much smaller component.
Among users and maintainers of the PNG and MNG formats, APNG had a lukewarm reception. In particular, PNG was conceived to be a single-image format. APNG hides the subsequent frames in PNG ancillary chunks in such a way that APNG-unaware applications would ignore them, but there are otherwise no changes to the format to allow software to distinguish between animated and non-animated images. Some of the main concerns arising from this were the inability of applications to negotiate for PNG and APNG, or distinguish between PNG and APNG once received, or for legacy software to even inform users that there are additional frames. Glenn Randers-Pehrson spearheaded efforts to reconcile the PNG purists' position with that of APNG proponents by recommending changes to APNG's format and proposing the use of a unique MIME type (e.g., video/png), but the APNG proponents only added the different MIME type (image/apng) while insisting on the use of the .png extension instead of .apng, leading to the format not being approved by the PNG Development Group.
The PNG Development Group rejected APNG as an official extension on April 20, 2007, and there have been several subsequent proposals for a simple animated graphics format based on PNG using several different approaches. However, since September 14, 2021, the PNG Working Group has been chartered by the World Wide Web Consortium (W3C) to maintain and develop for the PNG specification, and the first public working draft of PNG Specification (Third Edition) was published on October 25, 2022, adding APNG extensions to the core PNG specification. The Candidate Recommendation was published on September 21, 2023.
On June 24, 2025 it was finally elevated to the Recommendation final status by the W3C.
The APNG specification follows the PNG File format introducing three new ancillary chunks:
Sequence numbers apply to both frame control and frame data chunks, which together follow a common sequence, thus enabling the order and timing of frames to be recovered should an APNG-unaware PNG editor re-order them as allowed by PNG chunk ordering rules.
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APNG AI simulator
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APNG
Animated Portable Network Graphics (APNG) is a file format which extends the Portable Network Graphics (PNG) specification to permit animated images that work similarly to animated GIF files, while supporting images with a higher color depth and full alpha transparency not available for GIFs. It also retains backward compatibility with non-animated PNG files.
The first frame of an APNG file is stored as a normal PNG stream, so most standard PNG decoders are able to display the first frame of an APNG file. The frame speed data and all of the subsequent frames are stored in extra chunks (as provided for by the original PNG specification). APNG competed with Multiple-image Network Graphics (MNG), a comprehensive format for bitmapped animations which was created by the same team as PNG and is obsolete. APNG's advantages over MNG are its smaller library size and its compatibility with older PNG implementations.
The APNG specification was created in 2004 by Stuart Parmenter and Vladimir Vukićević of the Mozilla Corporation to allow for storing the animations needed for interfaces such as throbbers. In May 2003, Mozilla had scrapped support for MNG animations, which provides a superset of APNG functionality, citing concerns about the large file size required for the expansive MNG decoder library (300 KB); the APNG decoder, built on the back of the PNG decoder, was a much smaller component.
Among users and maintainers of the PNG and MNG formats, APNG had a lukewarm reception. In particular, PNG was conceived to be a single-image format. APNG hides the subsequent frames in PNG ancillary chunks in such a way that APNG-unaware applications would ignore them, but there are otherwise no changes to the format to allow software to distinguish between animated and non-animated images. Some of the main concerns arising from this were the inability of applications to negotiate for PNG and APNG, or distinguish between PNG and APNG once received, or for legacy software to even inform users that there are additional frames. Glenn Randers-Pehrson spearheaded efforts to reconcile the PNG purists' position with that of APNG proponents by recommending changes to APNG's format and proposing the use of a unique MIME type (e.g., video/png), but the APNG proponents only added the different MIME type (image/apng) while insisting on the use of the .png extension instead of .apng, leading to the format not being approved by the PNG Development Group.
The PNG Development Group rejected APNG as an official extension on April 20, 2007, and there have been several subsequent proposals for a simple animated graphics format based on PNG using several different approaches. However, since September 14, 2021, the PNG Working Group has been chartered by the World Wide Web Consortium (W3C) to maintain and develop for the PNG specification, and the first public working draft of PNG Specification (Third Edition) was published on October 25, 2022, adding APNG extensions to the core PNG specification. The Candidate Recommendation was published on September 21, 2023.
On June 24, 2025 it was finally elevated to the Recommendation final status by the W3C.
The APNG specification follows the PNG File format introducing three new ancillary chunks:
Sequence numbers apply to both frame control and frame data chunks, which together follow a common sequence, thus enabling the order and timing of frames to be recovered should an APNG-unaware PNG editor re-order them as allowed by PNG chunk ordering rules.