Fixes / Excel · Checked

Excel "links to external sources that could be unsafe": fix

Short answer

The file has formulas or other items that pull data from a different workbook, and Excel asks before fetching it. Click Don't Update if you don't know the source. To remove the prompt for good, open Data > Workbook Links (older versions: Data > Edit Links) and choose Break links, which turns the linked formulas into fixed values.

What this message means

Excel shows this when you open a workbook that references cells in another file, such as a formula like ='[Budget.xlsx]Sheet1'!A1, or a link hidden in a named range, chart, data validation list or conditional formatting rule. Updating makes Excel open or read that other file to get fresh numbers. Excel calls it "could be unsafe" because a link can point to a file you don't control. It is a warning, not an error. Choosing Don't Update keeps the values last saved in the file, and nothing in your workbook breaks.

Common causes

CauseHow to tell
Data was copied from another workbook and Excel pasted it as linked formulasClicking a cell shows a formula containing a file name in square brackets, such as ='[Sales Q2.xlsx]Summary'!B4, or a full path ending in .xlsx or .xls.
A sheet or chart was moved or copied in from another workbook, bringing named ranges with itFormulas > Name Manager (Ctrl+F3) lists names whose Refers To column starts with a path or [filename]. These often show a #REF! error too.
A chart, shape, text box or button still points at the old fileSelecting a chart series shows =SERIES('[Old.xlsx]Sheet1'!...) in the formula bar, or a shape's assigned macro or linked cell names another workbook.
A data validation list or conditional formatting rule refers to another workbookFind & Replace finds nothing in formulas but Workbook Links still lists a source. Home > Conditional Formatting > Manage Rules (This Worksheet) or Data > Data Validation shows a reference to another file.
The linked source file has been moved, renamed or is on a network drive you can't reachClicking Update produces a second message saying links can't be updated, and the Workbook Links pane shows an error status for the source.

How to fix it

1. Decide on this one prompt safely

  1. If you don't know who made the file or what it links to, click Don't Update. The workbook opens with the values last saved in it.
  2. If you expect the file to pull live numbers from another workbook you trust (a shared budget file, for example), click Update.
  3. If the source is on a network drive or SharePoint, connect to it first (VPN or sign in), then reopen the file and click Update.

2. Break the links so the prompt stops for good

Excel for Microsoft 365 and Excel 2021/2024 on Windows use the Workbook Links pane. Excel 2019 and earlier (and some Mac builds) use Data > Edit Links, with a Break Link button.

  1. Save a backup copy first. Breaking links can't be undone in desktop Excel.
  2. Go to Data > Queries & Connections > Workbook Links (older versions: Data > Edit Links).
  3. Look at the listed source files to confirm they are ones you don't need live data from.
  4. Select More Commands (...) next to a source and choose Break links, or click Break all.
  5. Save the workbook, close it and reopen it. Formulas that used those sources are now plain values.

3. Find links that Break links can't remove

Windows and Mac. Menu names are the same; on Mac use Cmd+F instead of Ctrl+F.

  1. In the Workbook Links pane, select More Commands (...) next to the source and choose Find next link to jump to cells that use it.
  2. Press Ctrl+F, click Options, set Within to Workbook and Look in to Formulas, search for .xl and click Find All. Also try searching for [ and http.
  3. Open Formulas > Name Manager (Ctrl+F3), sort by Refers To and delete names pointing to another file or showing #REF!.
  4. Check charts: click each data series and look at the =SERIES formula for a file name. Change it with Chart Design > Select Data.
  5. Check Home > Conditional Formatting > Manage Rules (set Show formatting rules for to This Worksheet) and Data > Data Validation on each sheet.
  6. If you still can't find it, copy sheets one at a time into a new workbook and reopen each copy to see which sheet brings the prompt back.

4. Keep the links but stop the question in this workbook

Setting is saved in the workbook and applies to everyone who opens it.

  1. Go to Data > Queries & Connections > Workbook Links.
  2. Expand Refresh settings (older versions: Edit Links > Startup Prompt).
  3. Choose Always refresh to update silently, or Don't refresh (older wording: Don't display the alert and don't update automatic links) to keep saved values without asking.
  4. Save the workbook. With Don't refresh, update later from the Workbook Links pane with Refresh all.

5. Turn off the question for every workbook you open

Excel for Windows. The setting applies only to your user account, not to other people who open the same files.

  1. Go to File > Options > Advanced.
  2. Under General, clear Ask to update automatic links.
  3. Click OK. Links in every workbook you open will now update automatically without a message.
  4. Only do this if you trust the files you open. Excel still warns about links that are broken or invalid.

6. Check the Trust Center policy for workbook links

Excel for Windows. On work PCs this may be locked by your IT department's policy.

  1. Go to File > Options > Trust Center > Trust Center Settings > External Content.
  2. Under Security settings for Workbook Links, check which option is selected.
  3. Prompt user on automatic update for Workbook Links is the default and safest choice. Disable automatic update of Workbook Links shows a yellow Security Warning bar with Enable Content instead.
  4. If the options are greyed out, the setting is managed by your organization. Ask IT rather than changing it.

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Still not fixed?

If Workbook Links still lists a source after you've broken links and checked names, charts, validation and conditional formatting, the reference is probably in a hidden defined name (Name Manager doesn't show hidden names), a PivotTable data source (PivotTable Analyze > Change Data Source), or an object's assigned macro. Save a copy as .xlsx, rename it to .zip, and search the xl/externalLinks folder and xl/workbook.xml to see the exact path. On a work network, your IT help desk can confirm whether a Trust Center policy is forcing the prompt, or can restore access to the moved source file.

Questions people ask

Is it safe to click Update?

It is safe if you know and trust the source workbook, for example a colleague's shared file on your company drive. If the file came from outside your organization or you don't recognize the source, click Don't Update. Your saved values stay the same.

What happens if I click Don't Update?

Excel opens the file using the values saved the last time the source was read. Nothing is deleted. The numbers may just be out of date.

Why does the message keep appearing after I broke all the links?

Break links only converts cell formulas. Links stored in named ranges, charts, data validation, conditional formatting or shapes stay behind and keep triggering the prompt. Use Find next link, Name Manager and the chart checks to remove them.

How do I find which cell has the external link?

Open Data > Workbook Links and use Find next link next to the source, or press Ctrl+F, set Within to Workbook and Look in to Formulas, and search for .xl. The Find All results list every matching cell.

Does turning off "Ask to update automatic links" affect other people?

No. That option in File > Options > Advanced applies only to your Excel on your computer. To change the behavior for everyone who opens a particular file, set Refresh settings in that workbook's Workbook Links pane.

Sources

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