Can you play Helldivers 2 solo?
Yes — set your session to Friends Only (or invite-only) before you drop, and no one else can join. You still need a constant internet connection, and on PS5 an active PlayStation Plus subscription, because the game has no offline mode.
Soloing works from the tutorial to the hardest difficulties, but two things you can't get around alone are the internet requirement and the two-player bunker doors.
Yes. Before deploying, set your game session to Friends Only (or invite-only) in the ship menu, and the matchmaker stops putting anyone else in your squad — you drop, fight and extract completely alone, on any difficulty you've unlocked.
What soloing doesn't get you out of is the internet. Helldivers 2 has no offline mode: every mission runs against Arrowhead's servers, win or lose, whether you're squadded with strangers or not. On PS5 that also means you need an active PlayStation Plus subscription even to play by yourself — Sony treats the always-online session as multiplayer regardless of who's in it. PC players don't need PS Plus at all.
Difficulty doesn't scale down for a solo Helldiver: enemy numbers and objective counts are the same as a four-player drop, just with nobody to split them with. That makes picking the right loadout matter more — check the weapons and armor pages before you commit to a build, since a solo run punishes a weapon that's weak against one enemy type harder than a squad run does.
The one thing solo genuinely can't do without help is open a bunker — the vaults locked behind two side-by-side doors that need someone pressing each one at the same time. The Control Group Warbond's Warp Pack stratagem lets a lone player teleport straight through the door and loot the bunker anyway, but without it you need a second Helldiver, an SOS beacon call, or one of the community's mech-based workarounds. None of this touches Major Orders or the war effort across the game's 281 planets — those track your solo contributions exactly like anyone else's.