THUMBDATA4 file extension is associated with Android operating system. Android was developed by Google in collaboration with Open Handset Alliance as an operating system for mobile devices such as smartphones or tablets.

THUMBDATA4 is a temporary file that stores image thumbnails used by Gallery app. Thumbnails are typically generated for stored pictures and other images or multimedia. Thumbnails allow faster loading times of images indexed by the system. Each THUMBDATA4 file is augmented with "--" characters follow by a random number.