What is confirmed
heatwarped.com includes a Compete Online section describing challenges against other players. That is an Official website claim.
The Steam store page currently still lists Single-player among features. Both facts are true at verification time and should be stated together.
What is still unknown
Sealime has not yet documented player count, matchmaking, co-op, PvP structure, lobby systems, online free roam, cross-play, or whether online uses dedicated servers or peer-to-peer. This page stays short until those details exist.
FAQ
Does Heatwarped have multiplayer?
Heatwarped's official website advertises online challenges against other players. The current Steam feature list still shows Single-player. Exact online mode structure is undocumented.
Is Heatwarped online free roam confirmed?
No official source checked for this page documents online free roam, lobbies, or matchmaking details yet.
Does Steam say Heatwarped is multiplayer?
Steam currently lists Single-player among store features. That listing coexists with the official website Online section and should be read together, not ignored.
Related: Heatwarped gameplay.