PNG itself does not support animation.
MNG is an extension to PNG that does; it was designed by members of the PNG Group.
MNG shares PNG's basic structure and chunks, but it is significantly more complex and has a different file signature, which automatically renders it incompatible with standard PNG decoders.

The complexity of MNG led to the proposal of APNG by developers of the Mozilla Foundation.
It is based on PNG, supports animation and is simpler than MNG.
APNG offers fallback to single-image display for PNG decoders that do not support APNG.
However, neither of these formats is currently widely supported.
APNG is supported in Firefox 3.0 and up, Pale Moon (all versions), and Opera 9.5, but since Opera changed its layout engine to Blink, support was dropped.
The latest version of Safari on iOS 8 and Safari 8 for OS X Yosemite support APNG.
Chromium 59.0 has added APNG support, then Opera added back in 46.0.
The PNG Group decided in April 2007 not to embrace APNG.
Several alternatives were under discussion, ANG, aNIM/mPNG, "PNG in GIF" and its subset "RGBA in GIF".
PNG itself does not support animation. MNG is an extension to PNG that does; it was designed by members of the PNG Group. MNG shares PNG's basic structure and chunks, but it is significantly more complex and has a different file signature, which automatically renders it incompatible with standard PNG decoders.
The complexity of MNG led to the proposal of APNG by developers of the Mozilla Foundation. It is based on PNG, supports animation and is simpler than MNG. APNG offers fallback to single-image display for PNG decoders that do not support APNG. However, neither of these formats is currently widely supported. APNG is supported in Firefox 3.0 and up, Pale Moon (all versions), and Opera 9.5, but since Opera changed its layout engine to Blink, support was dropped. The latest version of Safari on iOS 8 and Safari 8 for OS X Yosemite support APNG. Chromium 59.0 has added APNG support, then Opera added back in 46.0. The PNG Group decided in April 2007 not to embrace APNG. Several alternatives were under discussion, ANG, aNIM/mPNG, "PNG in GIF" and its subset "RGBA in GIF".
Portable Network Graphics