APNG (Animated PNG) Detector

No. Nothing is uploaded. The file is read and parsed entirely in your browser using JavaScript, so the image never leaves your device.

APNG (Animated PNG) is an extension of the PNG format that stores a short animation while staying backward compatible with regular PNG viewers. It adds an acTL control chunk plus fcTL frame chunks and fdAT frame data, so an old decoder simply shows the first image and ignores the rest.

It walks the PNG chunk stream and looks for the acTL (animation control) chunk. A PNG is treated as animated only when that chunk is present. The acTL data also carries the number of frames and the number of times the animation should play.

The acTL chunk stores num_plays. A value of zero means the animation loops forever, which is why the tool shows 'Loops forever' for zero. Any positive number is the exact count of times the animation plays before stopping.

The acTL chunk declares num_frames, while each rendered frame has its own fcTL chunk. They normally match. The tool shows both so you can spot a malformed or truncated file where the declared count and the actual fcTL count disagree.

It depends on chunk order. If the first fcTL comes before the IDAT image data, the default image is the first animation frame. If IDAT comes first, the default image is only a static fallback for non-APNG viewers and is not counted in the loop.