The Accidental Dependency
One of the most frustrating errors in Microsoft Excel is the dreaded “This workbook contains links to one or more external sources that could be unsafe” security warning. This usually happens when you are working with multiple spreadsheets open at the same time. If you type a simple formula like =A1+B1, but you accidentally click on cell B1 in a different open workbook instead of your current one, Excel silently creates a permanent “External Link” between the two files. Even if you later delete the formula, the hidden link often remains embedded in a named range or data validation rule. When you email your spreadsheet to a colleague, they will receive an error because they do not have the second workbook on their computer to fulfill the linked data.
How to Break Existing External Links
If your workbook is already plagued by the security warning on startup, you must locate and destroy the external links.
1. Open the problematic Excel spreadsheet.
2. Click on the Data tab in the top ribbon menu.
3. In the “Queries & Connections” group, look for a button labelled Edit Links. (If this button is greyed out, Excel does not detect any external file links).
4. Click Edit Links to open the dialogue box showing every external file your spreadsheet relies on.
5. Select the file(s) from the list.
6. Click the Break Link button on the right side of the window.
7. A warning will appear stating that breaking the link will convert the formulas into their current calculated values (meaning a formula that resulted in “50” will become a hardcoded “50”). Click Break Links to confirm.
8. Save the file. The annoying startup prompt should now be gone.
How to Stop the Annoying Update Prompt
If you want the external links to exist (because you are pulling data from a master company sheet), but you are tired of clicking “Update Links” every single time you open the file, you can suppress the prompt.
1. Go back to Data > Edit Links.
2. Click the Startup Prompt… button at the bottom left of the window.
3. You have two options to suppress the pop-up:
- Select Don’t display the alert and don’t update automatic links if you want the file to open quickly and you will manually update data later.
- Select Don’t display the alert and update links if you want Excel to pull the fresh data silently in the background without bothering you.
4. Click OK and save the workbook.