A SMSEC file is a space sector file used by StarMade, an open-universe space simulation sandbox game. It contains an exported sector, which is a three-dimensional cube-shaped area organized into a grid that makes up the space in StarMade where a player can fly, fight, build, or trade.

StarMade's allows you to explore the universe finding materials to upgrade your ship and fend off attacks from enemies. In the game you navigate through sectors, which may contain space stations, other ships, asteroids, planets, stars, or nothing at all. These sectors are the smallest units of space in the StarMade universe. They are configurable but approximately 5,000 meters on each side. Sectors are contained in 16x16x16 areas known as systems in the game. There are several types of sectors in StarMade, with each one providing different challenges: Space station - May be a trading shop, pirate station, abandoned. Planet - Takes up a whole sector but can only spawn within systems that have a star. Asteroid belt - Floating rock formations that contain resources. Star - Hot balls of plasma that are dangerous to approach. Void - Contains no life or activity, which allows space stations or ships to be build without interference. StarMade allows you to export and import sectors for sharing purposes. When you export a sector, an SMSEC file is created to store all the information of the sector. The file is meant to be opened only within StarMade but it is compressed in the Zip format, which allows you to manually extract its contents with a utility such as 7-Zip or WinZip.