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

Symptoms
In Microsoft Excel 2013 and later versions, when you open multiple spreadsheets, they all open in the same instance of Excel. However, in some situations, such as when you're working with large Excel spreadsheets, you may want to open each one in a new instance. This article explains how to do that by configuring a registry key.

Note This method works only when you use the Excel icon to open the application. If you use File Open within the Excel application or double-click a file in Windows Explorer, the files will still open in the same instance as designed.

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

Note If you are using the Large Address Aware option (see the "More Information" section), this limit may be increased.
Resolution
To change the default setting, install the latest version of Office (build numbers referenced in the following table), and then add the key to the registry. The versions of Office that have the update include the following:
VersionRelease dateBuild number
Office 365 for 2016 (Current Channel Subscribers)May 3, 2016 Build 16.0.6868.2060
Office 365 for 2013June 7, 2016Build 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

Important 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:

    HKCU\Software\Microsoft\Office\16.0\Excel\Options
  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, press and hold (or right-click) DisableMergeInstance, and then select Modify.
  7. In the Value data box, 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.

Note There are some known issues in opening each Excel spreadsheet in its own instance. For example, see You cannot paste any attributes into a workbook in another instance of Excel.
LAA Performance XL instance opening out of memory resources
Properties

Article ID: 3165211 - Last Review: 06/28/2016 02:19:00 - Revision: 3.0

Excel 2016, Microsoft Excel 2013, Excel for Office 365

  • KB3165211
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