A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
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"AutoSave is enabled when working on a file that is saved to OneDrive, OneDrive for Business, or SharePoint Online. If the file is saved to another location, then AutoSave is disabled. This will happen if your file is on a SharePoint On Premises site, a file server, or saved to a local path like C:.
There are other reasons AutoSave could be disabled as well. For example, if your file is in an older format like .xls, .ppt, or .doc., it will be disabled. It will also be disabled if your presentation is in slide show mode, or if your workbook contains password protection. If AutoSave is disabled, you can always hover over the AutoSave switch and a tooltip will tell you why it's off."