Our Tiles API and Static Maps API support a variety of image formats. We recommend using .png for most usecases, but you can choose other formats for special situations.
the standard image format, equivalent to png256
256 colour PNG
128 colour PNG
64 colour PNG
32 colour PNG
JPEG compressed image format, equivalent to jpg80
JPEG, quality 70
JPEG, quality 80
JPEG, quality 90
The file size of an image is generally smaller with few colours (PNG files) and lower quality (JPG files), but the visual artefacts become fairly obvious. In particular, the particular colours used for each map image is calculated per-tile, after anti-aliasing, so it can be common for different tiles to have different available colours. Small colour palettes are best reserved for map styles that have only a few colours to begin with.