Interlaced  thumbnails offer a better viewing experience, especially on slow connections, as a slightly lower-quality but recognizable version of the image is displayed much sooner in the loading process.
- T119797: Serve low-res images by default to users on slow or metered mobile connections
- T42663: Add interlace info to file metadata
- T87184: Establish a user testing framework for perceived speed
 Often also called progressive loading; but the ability to render an image while loading, in a non-interlaced, top-to-bottom way, is also often called progressive loading, so that terminology can be confusing.