Why won't Steam Knight Online start?

Steam Knight Online startup symptoms
SymptomCauseFix
Launcher closes silently after patching By design (NTTGame support article) Start the game again from Steam
Drops to desktop after START Steam closed, game started outside Steam, or Steam info unreadable (-99) Sign in to Steam, launch from the library
Closes before XIGNCODE finishes Security software or a damaged XIGNCODE file XIGNCODE steps
Antivirus deletes KnightOnLine.exe Heuristic detection after an update Verify files, add the game folder as an exclusion
Stuck on a black screen Missing or damaged files, display mode Verify files, change window mode/DX
Won't start during maintenance Updates don't download during maintenance Wait for maintenance to end

Step-by-step fix

  1. Open Steam and make sure you're signed in; launch the game from your Steam library.
  2. If it closed after an update, start it once more; per NTTGame's support article that's normal.
  3. Library → Knight Online → Properties → Installed Files → "Verify integrity of game files".
  4. If your antivirus or firewall blocks the game, add the game folder as an exclusion; don't turn the antivirus off.
  5. If the XIGNCODE window never fills, follow the official steps in XIGNCODE3 error.
  6. Still not starting? Open a ticket on the support site with a screenshot.

Antivirus deletes KnightOnLine.exe as a virus

Players report Windows Defender and some antivirus programs quarantining the game's exe as a "Trojan" or "Malware" after updates. First check that the file really is in the game folder of your Steam library, then verify game files and add only the game folder as an exclusion. Never run a copy downloaded from outside Steam. If you think the alert is wrong, you can report the file to the antivirus vendor.

Steam Deck, Linux and virtual machines

The game's anti-cheat, XIGNCODE, won't let it open in virtual environments; there's no official Steam Deck or Linux support, and players say XIGNCODE stops it from starting. Play on a regular Windows install.

The game opens but FPS is low or it crashes on DX11

NTTGame improved FPS problems caused by Windows 11 24H2 on some systems in April 2025. If DX11 crashes in crowded areas, switch to DX9: Knight Online DX11 or DX9? Best stable DirectX settings; for FPS see How to increase FPS in Knight Online: settings that help most.

FAQ

Steam Knight Online closes when I press START. Why?
Usually Steam isn't running or the game was started outside Steam. Sign in to Steam and launch from the library; if it continues, see the -99 steps.
Knight Online closes after updating. Is it broken?
No. According to NTTGame the client closing without warning after a patch is by design; start it again.
Is KnightOnLine.exe a virus?
If it comes from the game folder in your Steam library, it's the game's own file; alerts are usually heuristic detections after updates. Don't run a copy from outside Steam.
Does Steam Knight Online run on Steam Deck?
No, there's no official support, and players say XIGNCODE keeps it from starting.

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