Elden Ring EasyAntiCheat Error — How to Fix It

What it means

On PC, Elden Ring's online mode runs through EasyAntiCheat (EAC), and when EAC won't start you get errors like 'EasyAntiCheat is not installed', 'Untrusted system file (start_protected_game.exe)', or a generic 'An EasyAntiCheat error has occurred'.
The usual causes are a broken or missing EAC install, antivirus quarantining EAC files, or a mod (Seamless Co-op, ReShade, overlays) clashing with it.
The game still runs offline if you launch it without EAC — the error only blocks the online service.

Affected Models

Elden Ring on PC (Steam) — EAC is PC-only
Elden Ring: Shadow of the Erdtree on PC
Note: consoles don't use EasyAntiCheat, so this doesn't apply there

Common Causes

EasyAntiCheat not installed or its install got corrupted
Antivirus or Windows Defender quarantining EAC files
Mods present — Seamless Co-op replaces EAC, and ReShade/overlays can trip it
Game files damaged after an update
Windows missing updates, or system files genuinely modified
EAC service blocked from running (disabled service, permissions)

How to Fix It

Reinstall EasyAntiCheat.

Go to the Elden Ring install folder (Steam > right-click Elden Ring > Manage > Browse local files), open the EasyAntiCheat folder, and run EasyAntiCheat_Setup.exe.
Choose Elden Ring, click Repair (or uninstall then install).
This fixes most EAC errors on its own.
Whitelist the game in your antivirus.

Add the Elden Ring folder — and especially start_protected_game.exe and the EasyAntiCheat folder — to your antivirus and Windows Defender exclusions.
Restore anything they've already quarantined.
Antivirus eating EAC files is the classic cause of 'untrusted system file'.
Remove mods if you're not using Seamless Co-op.

If you mod the game, EAC and the mods fight.
Seamless Co-op intentionally launches without EAC (so you can't use it for normal online play) — if you want vanilla online, fully remove all mods, including ReShade and overlay tools, then verify files.
Don't try to run mods and EAC together.
Verify game files and update Windows.

Steam: right-click Elden Ring > Properties > Installed Files > Verify integrity of game files.
Then run Windows Update — EAC checks system file integrity, and a half-patched Windows can read as 'modified'.
Reboot afterward.
Run as administrator and check the EAC service.

Right-click the game's launcher and Run as administrator.
Press Win+R, type services.msc, find 'EasyAntiCheat' and make sure it isn't disabled (set it to Manual and start it).
If nothing works, a clean reinstall of the game — folder deleted, then reinstalled — gives you a fresh EAC too.

Frequently Asked Questions

Can I play Elden Ring offline if EasyAntiCheat won't work?

Yes.
EAC only guards the online service; the single-player game runs without it.
From Steam you can launch Elden Ring and choose 'Play Elden Ring' (with EAC) or 'Launch Elden Ring' (offline, no EAC) — pick the offline option to keep playing while you sort EAC out.
Just remember you can't summon, be invaded, or see messages until EAC is working again.