"Screeps has one-of-a-kind gameplay. This is a strategy sandbox MMO game for programmers. Players oversee a colony. They are in charge of securing resources by harvest or trade"
"Trove is a voxel adventure MMO that has robust sandbox gameplay. The world is made of destructible blocks. If you don’t like the looks of something, just take it down."
"Archeage is a fantasy sandbox MMORPG that’s perfect for those who are into building and crafting. The game offers you the skills and tools to create anything from simple items to castles."
"Boundless is a sandbox MMO with voxel-based graphics. The gameplay proposes a space adventure that gives players the chance to discover and colonize planets. "
"Fractured is the sandbox isometric MMO where you don’t have to level up in order to access the best content. The unique progression system is based on reputation and skills."