msvcp140_atomic_wait.dll: a genuine Visual C++ library, or a file only using its name?

What msvcp140_atomic_wait.dll does

msvcp140_atomic_wait.dll extends msvcp140.dll, Microsoft's C++ Standard Library runtime. It holds 32 functions that were added after msvcp140.dll had to stay frozen for older programs: waiting and waking on atomic variables, a thread pool for parallel algorithms, and the C++ time zone database. A program built with a recent Visual Studio loads it whenever it uses one of those features.

The file does not open network connections or start at sign-in. Its import table lists only other Visual C++ runtime files and Windows libraries, and at run time it loads Windows' own icu.dll to read time zones and reads the leap second list from the registry key SYSTEM\CurrentControlSet\Control\LeapSecondInformation. Anything a copy does beyond that comes from a different file with the same name.

About .dll files. A .dll file is a library: it cannot run on its own and is loaded into a program's process. It does not appear in Task Manager under its own name; Process Explorer shows which process loaded it.

How to check a copy of msvcp140_atomic_wait.dll

Three questions settle it: where the file is, who signed it and which program loads it. A library never appears in Task Manager under its own name, so use these checks.

1. List every copy and where it sits. Run this in PowerShell. Copies in Windows, Program Files, WindowsApps and a game's folder are normal. Look closer at copies under AppData, Temp, Downloads or ProgramData, especially recent ones beside an .exe you do not recognise.

   Get-ChildItem -Path C:\ -Filter msvcp140_atomic_wait.dll -Recurse -ErrorAction SilentlyContinue | Select-Object FullName, Length, LastWriteTime

2. Check the signature of a copy you are unsure about. Status must be Valid and the signer must be Microsoft. NotSigned, HashMismatch or another company's name means the file is not an unmodified Microsoft build.

   Get-AuthenticodeSignature "C:\path\to\msvcp140_atomic_wait.dll" | Format-List Status, SignerCertificate

3. Look at the size. Genuine builds are small: the current official files are 57,792 bytes (x64), 57,272 bytes (x86) and 89,952 bytes (ARM64), and the older builds indexed from Windows images are around 40 to 57 KB. A copy of several megabytes is not this library, whatever its name.
4. See which program loads it. In Process Explorer (Microsoft Sysinternals) open Find, Find Handle or DLL, and type msvcp140_atomic_wait.dll. Each result shows the process and the full path of the copy it loaded. A program running from Temp or AppData that loads its own copy deserves a look at what that program is.
5. Compare the checksum. Use the file check on this page. A match tells you which build you have; the signature check above tells you whether the file is genuine. Neither one says anything about the program sitting next to the file.

A valid Microsoft signature proves the DLL is genuine. It does not clear the folder or the other files in it.

Do you need msvcp140_atomic_wait.dll?

Keep the copies in Windows folders and in programs you installed: without them those programs stop starting. Remove only a copy that failed the checks above, together with what came with it.

1. Leave System32, SysWOW64 and program folders alone. These copies belong to the Visual C++ Redistributable or to the program that brought them. Deleting one breaks every program that loads it, and the file starts no process you could stop anyway.
2. To remove the runtime, uninstall the package, not the file. Open Settings, Apps, Installed apps and type “Visual C++”. Uninstalling “Microsoft Visual C++ 2015-2022 Redistributable” removes msvcp140_atomic_wait.dll with the rest of the runtime, but programs that need it will then fail to start.
3. Run a Microsoft Defender full scan on a suspicious copy. Open Windows Security, Virus and threat protection, Scan options, Full scan. Quarantine what it finds before deleting anything by hand.
4. Run the offline scan if something was found. Code loaded into a running program can hide while Windows runs. The offline scan restarts the PC and scans before Windows starts.

   Start-MpWDOScan

5. Delete the suspicious folder, not only the DLL. If a copy failed the signature check and sits next to an unknown .exe in Temp, AppData, Downloads or ProgramData, remove the whole folder and any scheduled task or startup entry that runs a program from it.

Warning signs

Known versions of msvcp140_atomic_wait.dll

A public DLL catalogue lists 2 versions of msvcp140_atomic_wait.dll, from 14.29.30037.0 to 14.29.30037.0, by Microsoft Corporation. Its copies are uploaded by users and not verified, so a checksum match identifies the version, while the digital signature tells you whether the file is genuine. Even a genuine file clears only the file, not the folder: attackers ship genuine libraries next to a program they abuse, so where the copy sits still decides whether it is safe.

Every version with its checksums, and how to fix msvcp140_atomic_wait.dll errors on uGetFix

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