Security software often flags these DLL files as "false positives" and moves them to quarantine, especially if they have been modified.
While steam_api64.dll is the standard official file, variations like steam_api64r.dll (often with an 'r' or other suffixes) are frequently associated with specific game modifications, cracks, or emulators used in non-licensed versions of games. Why is the File Missing? Common reasons for this error include:
If you are using a non-licensed copy of a game, the custom DLL required to run it might be missing or blocked by Windows Defender. How to Fix Steam-api64r.dll Errors Safely
A failed update or improper shutdown can corrupt the file.
Steam-api64r.dll File Download: Fix Missing DLL Errors Safely