Matchbox is a free and open source window manager for the X Window System. It is mainly intended for embedded systems and differs from most other window managers in that it only shows one window at a time. It is being used in the Maemo on Nokia Internet Tablets, the Neo 1973 smartphone based on Openmoko, the Vernier LabQuest handheld data acquisition device for science education, as well as on the XO-1 of the One Laptop Per Child Project. It has been replaced on later OLPC software builds by Metacity.