How Excel UNDO works with multiple workbooks

Overview

It is very common to have more than one Excel workbook open at a time.  

When using Excel's UNDO feature, it helps to know how that feature works.

Example

Here is an example where we have four separate workbooks open on our computer:

in cell A1 of Book1, we'll put the number 1:

Likewise, we'll place:

• the number 2 in Book2
• the number 3 in Book3
• the number 4 in Book4

Now, let's switch back to Book1 and hover over the UNDO button on the Excel title bar, as though we were about to click it:

Notice that what Excel is going to do is UNDO the typing we placed in Book4 !

Even though we are current sitting in Book1, Excel's UNDO feature works across all of the currently open workbooks.

Thus, Excel will UNDO in the reverse order of what we have changed - regardless of where each change was made in the various open workbooks.