Problem: Excel opened the first file quickly, but the second and subsequent files opened very slowly when launched externally (double click from Explorer or using excel.exe "file.xlsx").

Dear @ENRIC,

I hope you’re having a good day.

Thank you for taking the time to share such a detailed description of the issue and the steps you went through to isolate it.

From what you explained, I understand that Excel opens the first file quickly when launched from Explorer or via the command line, but starting with the second file the opening time becomes noticeably slower, while opening files from within Excel or using drag and drop remains fast. I also understand that this happens on a clean Windows and Office installation, does not affect Word, and is not resolved by reinstalling Office or adjusting security settings.

I really appreciate you documenting the root cause you identified around the Excel DDE registry handler and sharing the exact registry path and value that resolved the problem. This kind of detail is extremely helpful, especially since issues related to shell associations and DDE are not obvious and can easily be mistaken for general performance problems.

Thanks for contributing your findings and solution. This information will likely save a lot of time for others who run into the same symptoms and are trying to understand why Excel behaves differently depending on how files are opened.

Glad to hear the issue is resolved on your system and thank you again for sharing your experience with the community. Wishing you all the best.

Warm regards, 

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The described behavior is consistent with issues caused by Excel’s DDE/shell integration and other shell-related performance problems when opening files from Explorer rather than from inside Excel.

The context provides two relevant mitigation patterns, both based on registry changes that affect how Office and the Windows shell handle file opening and metadata:

1. For Office performance issues when opening from network or shell locations, enabling shell data caching is a documented workaround:
   1. Close all Office apps.
   2. Open regedit.
   3. Go to the key for the installed Office version, for example for Office 2021/2019/2016/Microsoft 365:
      • HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Open Find
   4. On the Edit menu, select New > DWORD (32-bit) Value.
   5. Name it EnableShellDataCaching.
   6. Set Value data to 1.
   7. Close Registry Editor and test Excel again.
   Any non‑zero value turns on caching and can improve responsiveness when opening files through Explorer or other shell mechanisms.
2. For DDE-related behavior, Excel’s handling of external links and DDE can be controlled via registry and Trust Center settings. While the context focuses on security (mitigating DDE attacks), it confirms that Excel’s DDE behavior is registry-driven:
   • To adjust DDE-related link handling:
     1. In Excel, go to File > Options > Trust Center > Trust Center Settings > External Content.
     2. Under Security settings for Workbook Links, set Disable automatic update of Workbook Links if testing whether live link/DDE traffic is contributing to the slowdown.
   • Or via registry (for the appropriate version number, e.g., 16.0 for Office 2016/2019/2021/Microsoft 365):
     • HKEY_CURRENT_USER\Software\Microsoft\Office\<version>\Excel\Security
       • Name: WorkbookLinkWarnings
       • Type: DWORD
       • Value: 2 (disables automatic update of workbook links, including DDE/OLE/external references).

These steps do not directly set the HKEY_CLASSES_ROOT\Excel.Sheet.12\shell\Open\ddeexec default value, but they operate on the same class of mechanisms (shell/DDE/open behavior and link handling) that affect how quickly Excel responds when launched from Explorer.

Because registry editing is involved, backing up the registry or creating a restore point before changes is recommended. Incorrect registry edits can cause system or application issues.

References:

• An Office program is slow or may stop responding (hang) when you open a file from a network location
• Securely opening Microsoft Office documents that contain Dynamic Data Exchange (DDE) fields