APNG is the animated extension of the PNG image format.

It has many advantages over GIF that you may not be aware of.
PNG
-has far better compression than GIF due to not being locked down to a proprietary compression scheme
-is not limited to 256 colors (GIF technically isn't either, but file sizes explode because you lose compression capability)
-is not limited to ~50 frames per second due to calculating frame display times in 10 millisecond increments; APNG instead has vastly finer frame rate control
-has gradient levels of transparency rather than a binary on/off, allowing some things that cannot be done easily in GIF, such as transition animations or blending colors between frames

Why use APNG instead of video formats like WebM?

APNG is especially good at traditional 2D animation.

WebM animates like most compressible video formats with heavy image compression over every frame and is able to achieve very small file sizes at the expense of visual fidelity. In contrast, like Animated GIF, APNG has the advantage of outright discarding visual information that doesn't change from one frame to another ("alpha compositing" or "delta-frame" compression) while being a lossless format. Alpha compositing allows animated formats to typically achieve smaller file sizes than lossless video formats when dealing with limited colors and animation. APNG additionally outperforms WebM's animation-supporting image format sibling, WebP at lossless animation.