If you open Excel files from Sharepoint, they by default open in Edit mode.
This sadly means, that whenever people interact with the sheet – for instance by filtering, this filtering will be saved. Extreeeemely annoying.
This may very well not be what you want. Fortunately, you can still set you Excel file to open by default in “Viewing” mode.
If you open Excel files in the native Application
As taken from here:
If you have a file that is sensitive to changes, you can force Microsoft Excel 365 / 2019 to prompt the user to open as Read Only whenever they attempt to open the file. Here’s how to enable this setting.
- File / Save As
- Type =”Excel Workbook”, More Options
- Tools / General Options
- “Read Only recommended”
- Save
If you open Excel files in the browser:
Taken from here:
If you want specific Excel workbooks to open in the view mode, open the said workbook in the browser, go to File>Info, click Protect Workbook.
Another way is to right-click the file in the library and select Preview.