Modern antivirus software often misidentifies steam-api64.dll as a threat because it injects code into running processes (a legitimate function for Steam overlay). When this happens, the AV quarantines or deletes the file without asking.
This is the most common cause. Anti-virus software (like Windows Defender, AVG, or Norton) sometimes identifies genuine game files as "false positives." Because the steam-api64.dll file interacts deeply with the system’s memory and network functions to communicate with Steam, antivirus heuristics can mistake it for malware or a trojan. If your antivirus quarantines the file, the game cannot find it. cod black ops 3 steam-api64.dll
In simple terms, when you launch BO3, the game looks for this file to confirm you own the game via Steam and to connect you to Valve’s servers. If Windows cannot find or read this file, the game aborts the launch. Modern antivirus software often misidentifies steam-api64