PNG

Portable Network Graphics

PNG is a raster image format with lossless compression. It appeared in 1996 as an open replacement for GIF and supports transparency (alpha channel).

Structure

After the eight-byte signature the file consists of chunks: IHDR with the dimensions and colour depth, one or more IDAT chunks with the compressed pixels and the final IEND. Every chunk carries a CRC checksum, so a damaged file is easy to detect.

When to use it

Diagrams, screenshots, logos and everything where sharp edges and transparency matter. For photographs PNG files are usually much larger than JPEG or WebP.