Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →The Baldur’s Gate 3 data mismatch warning means the launcher found files it considers unexpected or altered. It does not prove that one specific file is corrupt or that the game is unplayable. Check the launcher’s altered-files report first, then remove only confirmed unwanted leftovers or repair the installation through your storefront.
What the data mismatch warning means
Larian says the warning can be caused by mods, corrupt files, unknown data, old files left behind after patches, or other unexpected files in the game’s Data or bin folders. The warning alone does not identify which cause applies. It may appear without preventing the game from launching; a crash or failure to launch is a separate symptom that needs troubleshooting.
Larian’s instructions cover PC and Mac, but the file paths below are for Windows. Do not apply these Windows paths to a Mac or console version. See Larian’s data mismatch FAQ for platform-specific guidance.
1. Read the altered-files report before changing files
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Open
%LocalAppData%Larian StudiosLauncherCache. You can paste this path into File Explorer’s address bar.What’s actually slowing this PC down?
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Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy.#1 Best Overall
Baldur's Gate 3 - For Playstation 5 (Japan Import) (Multi Language)- Online multiplayer for up to four players - allows you to combine your forces in combat, and split your party to follow your own quests and agendas. Concoct the perfect plan together… or introduce an element of chaos when your friends least expect it
- Origin Character - offer a hand-crafted experience, each with their own unique traits, agenda, and outlook on the world. Their stories intersect with the entire narrative, and your choices will determine whether those stories end in redemption, salvation, domination, or many other outcomes
- Evolved turn-based combat - based on the D&D 5e ruleset. Team-based initiative, advantage & disadvantage, and roll modifiers join combat cameras, expanded environmental interactions, and a new fluidity in combat that rewards strategy and foresight
- Define the future of the Forgotten Realms - through your choices, and the roll of the dice. No matter who you play, or what you roll, the world and its inhabitants will react to your story
- Player-initiated turn-based mode - allows you to pause the world around you at any time even outside of combat. Whether you see an opportunity for a tactical advantage before combat begins, want to pull off a heist with pin-point precision, or need to escape a fiendish trap. Split your party, prepare ambushes, sneak in the darkness -- create your own luck!
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Find the report whose name identifies your platform and game version and ends in
_alteredFiles.txt. Steam and GOG use different platform labels, so look for the matching report rather than relying on a specific filename. -
Open the report and note the file names and locations it lists. Use those details to guide cleanup; do not delete files blindly.
2. Remove only unwanted mods or leftover files
If you previously installed mods or updated the game through several patches, inspect the locations Larian identifies. Make a separate copy of any mods or saves you want to keep before removing files. Do not delete saves or wanted mods as a general fix.
Rank #2
- Immersive RPG Experience: Dive into the highly-anticipated Baldur's Gate 3, a captivating role-playing game set in the iconic Dungeons & Dragons universe.
- Deluxe Edition: This premium edition includes the base game, exclusive stickers, and an official soundtrack to enhance your adventure.
- Epic Storytelling: Embark on an epic journey filled with complex narratives, challenging quests, and memorable characters.
- Tactical Combat: Engage in strategic, turn-based battles that require careful planning and execution of your party's abilities.
- Customizable Characters: Create and customize your own unique heroes, shaping their appearances, abilities, and personalities to fit your playstyle.
Check for old mod files
Review the game’s install folders DataMods and DataPublic, as well as the local AppData game Mods folder and your profile’s modsettings.lsx, where applicable. If you no longer want the mods and the report points to related files, remove the unwanted files or folders. Larian’s FAQ lists these locations and cleanup guidance.
Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsCheck for obsolete patch files
In the game install’s Data folder, look for files named Patch#_HF#.pak. Larian says files with a patch number below the current patch may be deleted; old patch hotfix files can also cause startup crashes. Patch numbers change, so confirm the current patch before deciding a file is obsolete.
3. Verify or repair the installation through your storefront
Use the client where you own or installed the game. Verification checks or restores expected installation files, but Larian cautions that it does not remove extra or duplicate files. It can help with a damaged or incomplete install, but it may not clear the cause of a mismatch warning if an unexpected file remains.
Rank #3
- Contains Enhanced Editions of Baldur's Gate, Baldur's Gate II, & Siege of Dragonspear
- Baldur's Gate - Since its original release in 1998, Baldur's Gate has set the standard for Dungeons & Dragons computer roleplaying games.
- Baldur's Gate II - Continue a journey started in Baldur's Gate: Enhanced Edition or create an entirely new character in this isometric Dungeons & Dragons roleplaying game.
- Baldur's Gate: Siege of Dragonspear - Adds a new chapter to the Bhaalspawn saga. The events occurring between Baldur's Gate and Baldur's Gate II are at last revealed in this 25-hour adventure.
| Storefront | Repair path | What to keep in mind |
|---|---|---|
| Steam | Library → right-click Baldur’s Gate 3 → Properties → Installed Files (called Local Files in some client versions) → Verify integrity of game files. | Steam checks expected game files; extra or duplicate files may remain. |
| GOG Galaxy | Select Baldur’s Gate 3 → game settings → Manage Installation → Verify / Repair. | GOG Galaxy checks or repairs expected installation files; extra or duplicate files may remain. |
Client labels can change. Larian’s official mismatch instructions describe these storefront workflows.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When the warning can be disregarded—and when it cannot
Larian says that having the Toolkit installed can trigger a data mismatch warning that can essentially be disregarded. That exception applies to the warning itself; if the game also crashes or will not launch, investigate that failure rather than assuming the Toolkit explains it.
A historical Larian forum post documents a false-positive Steam warning after a particular old hotfix, related to a stale manifest. That was specific to that patch period, not a current universal fix. Do not delete or replace manifest files based on that old workaround.
Rank #4
If BG3 still crashes or will not launch
If cleanup and storefront repair do not resolve the problem, contact Larian Support with a clear description of what happens and what you have already tried. Include steps that reproduce the issue and relevant save files or crash information when appropriate. For crashes, Larian’s mismatch FAQ specifically asks for a DxDiag report.
Use Larian’s bug-report instructions to prepare the information. Avoid renaming or deleting the broader local BG3 data folder as an early fix: it can contain saved games and settings. Larian’s PC startup troubleshooting FAQ explains that folder’s contents. Its separate advice about clearing LevelCache addresses problems usually associated with saving or loading, not the launcher’s mismatch warning.
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