How to force Excel to open in a new instance by default


In Microsoft Excel 2013 and later versions, when you open multiple workbooks, they all open in the same instance of Excel. However, in some situations, you may want to open each workbook in a new instance, such as:

  • You're working with large Excel workbooks.
  • You want to undo actions in only the active workbook.

This article explains how to do so by configuring a registry key.


This method works only when you use the Excel icon to open the application without selecting a file. If you use the follow ways, the workbooks will still open in the same Excel instance as designed:

  • You use File Open within the Excel application.
  • You select a file when you use the Excel taskbar icon to open the application.
  • You double-click an Excel workbook in Windows Explorer.

For more information about Excel instances, and how to start a new instance in other ways, see What are Excel instances.


By opening each workbook in its own instance, the workbook has a dedicated 2 gigabytes (GB) of memory to use. It's important if you are experiencing out-of-memory issues in a 32-bit version of Excel.


If you're using the Large Address Aware option, this limit may be increased.


To change the default setting, install the latest version of Office (build numbers referenced in the following table are the minimum builds required for that version), and then add the key to the registry. The versions of Office that have the update include:

Version Release date Build number
Office 2016 (Current Channel Subscribers) May 3, 2016 Build 16.0.6868.2060
Office 2013 June 7, 2016 Build 15.0.4833.1001
Excel 2013 (MSI) June 7, 2016 Build 15.0.4833.1000
Excel 2016 (MSI) June 7, 2016 Build 16.0.4393.1000


Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.

  1. Exit all instances of Excel.

  2. Start Registry Editor:

    • In Windows 10, click Start, type regedit in the Search box, and then select regedit.exe in the search results.
    • In Windows 8 or Windows 8.1, move the pointer to the upper-right corner, select Search, enter regedit in the search box, and then select regedit.exe in the search results.
  3. Locate and select the following registry subkey:


  4. On the Edit menu, point to New, and then select DWORD Value.

  5. Enter DisableMergeInstance, and then press Enter.

  6. In the Details pane, right-click DisableMergeInstance, and then select Modify.

  7. In Value data, enter 1, and then click OK.

More Information

32-bit versions of Excel 2016 can take advantage of the Large Address Aware (LAA) functionality after installation of the May 3, 2016, update for Outlook 2013 (KB3115031), build 16.0.6868.2060 for O365 Current Channel subscribers. This change lets 32-bit installations of Excel 2016 consume double the memory when users work on a 64-bit Windows OS. The system provides this capability by increasing the user mode virtual memory from 2 GB to 4 GB. This change provides 50-percent more memory (for example, from 2 GB to 3 GB) when users work on a 32-bit system. For more information about LAA, see Large Address Aware capability change for Excel.


There are some known issues in opening each Excel workbook in its own instance. For example, see You cannot paste any attributes into a workbook in another instance of Excel.