Need to check what's in a spreadsheet without opening Excel, or on a device that doesn't have it installed? Excel Viewer reads the file locally and shows every sheet as a simple table.
No, this is a viewer only. Properly supporting edits would mean recalculating formulas, which this tool doesn't attempt, so cell values aren't editable here. For a grid you can actually edit, try CSV Editor instead.
Each formula cell shows its last-calculated, formatted value, the same text Excel would display, rather than the formula itself. Nothing is recalculated.
Excel formats (.xlsx, .xls, .xlsm), CSV, and ODS all work. Very complex formatting, merged cells, and embedded charts or images aren't specially represented; the focus is on getting the data itself in front of you quickly.
No. The file is read and rendered entirely in your browser. Nothing about its contents is sent to a server.