How do I turn off AutoFill in Excel Online?

Put the mouse pointer over the bottom right-hand corner of the cell until it's a black plus sign. Click and hold the left mouse button, and drag the plus sign over the cells you want to fill. And the series is filled in for you automatically using the AutoFill feature.

Click File > Options. Click Advanced. Under Editing Options, check the Enable fill handle and cell drag-and-drop box.

Click File > Options. In the Advanced category, under Editing options, select or clear the Enable fill handle and cell drag-and-drop check box.

What is AutoFill? Excel has a feature that helps you automatically enter data. If you are entering a predictable series (e.g. 1, 2, 3…; days of the week; hours of the day) you can use the AutoFill command to automatically extend the sequence.