The definitive Map API buying guide
Raster Tile APIs deliver pre-drawn and pre-styled images of a particular area.
Opposite to that, Vector Tile APIs deliver the metadata, and the drawing actually takes place on the client-side - in the browser on a device.
Raster Tile APIs deliver pre-drawn and pre-styled images of a particular area. Raster Tiles are typically 256x256 pixels in size and are pre-generated and stored on map API servers. As the end-user interacts with the map (pan or zoom), map rendering SDK fetches the tiles from the map server, gathers and arranges them to form a credible overview of the Earth on the screen. Tiles are arranged vertically and horizontally in rows and columns, very much like floor tiles, hence the name.
Raster Tiles is a simple and tried and tested technology and works on all browsers and mobile devices. Because tiles are pre-generated and stored on map servers, they don't impact the performance besides the possible download time.
Because the images are pre-generated and stored on map servers, they cannot be customized on the client-side. Each change in tiles' appearance requires that the Map API vendors generate a new set and uploads it to a server. This is actually quite a time-consuming process and requires a lot of storage space. Nowadays, HiDPI/Retina displays are practically a standard, and they necessarily require bigger tiles.
Opposite to that, Vector Tile APIs deliver the metadata, and the drawing actually takes place on the client-side - in the browser on a device.
Modern Tile APIs deliver metadata information of a particular area instead of pre-drawn images and are called Vector Tile APIs. Instead of delivering pre-drawn images, they deliver the metadata of road networks, buildings, woods, rivers, etc.
Drawing those metadata in a browser or on a mobile device is up to a vector-friendly map software - map rendering SDK. SDK renders maps depending on specified style rules (style sheets), e.g., road thickness and color, font and size of road labels, entire color palettes, etc. An SDK and a client application decide what to draw (and how) or what not to draw. Because the drawing happens on a client-side, map appearance can even be adjusted on-the-fly (e.g., switch map to day or night mode).
Such map rendering SDKs use either OpenGL, WebGL, or HTML5 canvas, providing an exceptionally smooth and visually attractive experience for end-users, especially compared to raster (image) tiles.
Check how Compact Maps ticks the boxes of your Map API buying checklist!