opencl.dll: genuine Windows or driver file, or a copy that a program loads instead?

What opencl.dll does, and why there can be more than one

OpenCL is an open interface from the Khronos Group for running calculations on graphics chips and other processors. Video and photo editors, 3D renderers, scientific software and benchmarks use it. On Windows, a program that uses OpenCL loads opencl.dll, the OpenCL Client DLL. The file is an ICD loader: it reads from the registry which OpenCL drivers (installable client drivers) are installed, loads them and forwards every call to the driver of the device the program picked. The real work happens in that driver, which comes with the graphics driver package of each chip maker.

Windows ships its own opencl.dll, and Winbindex indexes it from Windows 10 1507 to Windows 11 26H1. Graphics drivers have often installed their own build of the same loader over it. That is why the file in System32 on one PC can carry another version, size and signer than on the next, and why System File Checker sometimes reports it as changed. Both are genuine; the difference is who supplied them.

Because opencl.dll is not one of the libraries Windows always takes from System32, a program looks in its own folder first. Some programs ship a copy there on purpose, so that they find a loader of the version they were built for. A file with the same name and the same exported functions, put next to the .exe, is loaded at start in place of the system copy.

The same position is open to harmful code. A copy in a program folder runs with the rights of that program and your user account: it can read and write files, open network connections and start other programs, while still passing the OpenCL calls on so that the program looks normal. So the question is never whether opencl.dll is a virus, but which opencl.dll you are looking at and who put it there.

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 tell a planted opencl.dll from the system copy

A DLL is not listed in Task Manager as a process, so use the folder, the file properties, PowerShell or Process Explorer.

1. Where the file is. List every copy with the command below. C:\Windows\System32, C:\Windows\SysWOW64 and the DriverStore folders hold the system's copies. A copy in a program folder should have arrived with that program's installer. A copy in Downloads, Temp, AppData or an empty folder has no normal reason to exist.

   Get-ChildItem C:\ -Recurse -Filter opencl.dll -ErrorAction SilentlyContinue | Select-Object FullName, Length, @{n='Version';e={$_.VersionInfo.FileVersion}}, @{n='Description';e={$_.VersionInfo.FileDescription}}

2. The Description field, the version and the size. Right-click the file, Properties, Details. A genuine loader says OpenCL Client DLL. Windows' own build has version 1.2.11.0 on Windows 10 and 3.0.1.0 or 3.0.6.0 on Windows 11, with the sizes in the facts table; a driver's copy has its own version and size. These fields can be copied, so this check only rules files out.
3. The digital signature. Windows' copy is signed by Microsoft through a catalog rather than inside the file, so the Properties window may show no Digital Signatures tab. A driver's copy is usually signed inside the file by the driver maker. PowerShell reads both kinds. Valid with Microsoft or your graphics chip maker as signer means genuine; NotSigned or an unknown signer means a third-party file.

   Get-AuthenticodeSignature 'C:\path\to\opencl.dll' | Format-List Status, SignatureType, SignerCertificate

4. What the program loads. Start the program, then open Process Explorer from Microsoft Sysinternals, choose Find > Find Handle or DLL, type opencl.dll and press Search. The path column shows which copy each process really loaded. A path outside the Windows folders means that copy is running inside the program.
5. Compare the hash with Microsoft's builds. Use the checker on this page: it computes the SHA-256 in your browser and compares it with the known Microsoft builds. A match is Microsoft's file. A system folder copy that does not match is most often your graphics driver's; confirm it by its signature.
6. Scan before you trust or delete. Run Microsoft Defender's full scan, and the offline scan if a detection keeps coming back. A detection on a copy outside the Windows folders deserves attention; a detection on the copy in System32 is rare and should be checked against the hash and signature first.

A match to a Microsoft build proves the file is Microsoft's. A file that does not match is not automatically malicious: graphics drivers install their own signed opencl.dll, and some programs ship one in their folder. What decides is who signed the file, where it sits and whether the program it sits next to really came with it.

Warning signs and what they mean

Everyday problems with opencl.dll

opencl.dll versions by Windows release

The newest build indexed for each release, and the update that delivered it. 53 Microsoft builds in total are known.

Known versions of opencl.dll

A public DLL catalogue lists 12 versions of opencl.dll, from 1.0.0.0 to 24.20.11021.1000, by Khronos Group. 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 opencl.dll errors on uGetFix

Questions people ask