ArcaOS is a proprietary operating system based on OS/2, developed and marketed by Arca Noae, LLC under license from IBM.

[6] Like OS/2 Warp, ArcaOS is a 32-bit[7] single user, multiprocessing,[8] preemptive multitasking[9] operating system for the x86 architecture.

[12] ArcaOS supports symmetric multiprocessing systems with up to 64 processor cores, although it is recommended to disable hyperthreading.

[38] ArcaOS supports serving and accessing CIFS/SMB shares using the open source Samba project, and provides a graphical utility named ArcaMapper to manage configuration.

[39] NetDrive for OS/2 provides access to a variety of additional filesystems such as NTFS and NFS via its own IFS driver.

[4][49] Some of the planned features for Blue Lion announced at the time were:[4] The name "ArcaOS" was first published in a TechRepublic article[52] on May 26, 2016, while the arcaos.com domain was registered December 20, 2015.