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There is no confirmed, code-specific fix for Dev Error 356 in Call of Duty: Modern Warfare II on PC. Activision’s published PC guidance covers crashes generally, not this error code. Try the low-risk steps below in order; they are troubleshooting suggestions, not guaranteed repairs.
What Dev Error 356 means
Players report Dev Error 356 in Modern Warfare II, but Activision’s reviewed support pages do not define the code or identify a confirmed cause. Activision’s PC troubleshooting guidance and crash guidance address general problems rather than Error 356 specifically.
A third-party guide proposes possible explanations, including language packs, servers, or shader cache, but these are theories rather than established findings. Treat any fix aimed at one of those causes as a test, not a diagnosis.
Try these steps in order
- Close and reopen the game and launcher. Exit Modern Warfare II, then fully close Battle.net or Steam before launching the game again.
- Restart your PC. If the error returns, restart Windows and try the game once more. These basic restart suggestions come from third-party Error 356 guidance; no controlled success rate is established.
- Repair or verify the game files.
- Battle.net: Open the game’s page, select the gear icon beside the Play button, then choose Scan and Repair.
- Steam: In your Library, right-click Call of Duty: Modern Warfare II and select Properties > Installed Files > Verify integrity of game files.
Activision recommends repairing files through the relevant launcher. Client labels can change over time.
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- Restart shader optimization, if the option is available. Look in the game’s Graphics settings for a shader optimization restart control. The menu wording may vary by game build. Let shader preloading finish before playing; this is a reasonable troubleshooting test, not proof that shaders cause Error 356.
- Check for a service incident. If the error began suddenly or affects other players, check the Activision Online Services page before making repeated local changes. The available guidance does not establish that this code is normally caused by a server problem.
If the error keeps causing crashes
Move on to Activision’s general PC crash recommendations. These steps can help narrow down common crash conditions, but Activision has not confirmed them as Error 356-specific repairs.
- Close potentially conflicting background apps. Activision specifically mentions overlays, remapping tools, and recording software as examples of applications that may interfere.
- Update your graphics driver. Get the current driver for your graphics card from its manufacturer. Activision’s older article includes driver versions from 2022, so those version numbers should not be treated as current recommendations.
- Check the PC requirements. Compare your system with Activision’s published Modern Warfare II PC requirements.
- Review security software settings carefully. Activision’s general guidance discusses adding the game folder to an antivirus exception list where appropriate. Do not disable security protection wholesale.
- Submit a crash report. If the problem persists, use Activision’s PC crash guidance to report it.
What not to try first
The available official guidance does not tie Error 356 to a hardware shortfall or establish buying hardware, reinstalling Windows, deleting game folders, using a VPN, or reinstalling the game as a specific remedy. Start with the reversible steps above instead of making costly or disruptive changes without evidence that they address this code.
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Activision’s known-issues listing, updated February 27, 2026, displays some tracked problems and invites players to report issues not listed. Error 356 does not appear in the displayed list; that does not prove Activision has never received reports or that it is not tracked elsewhere. See Known Issues in Modern Warfare II for the current listing.
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