Excel Merge

Yes. Merging workbooks needs a server, so the files are sent over an encrypted connection. The copies there are deleted as soon as the result is sent back, unless you are signed in and asked to keep it.

Files in the order you arranged them, and within each file the sheets in their original order. Nothing is sorted.

The first keeps its name. Later ones get a number: Sheet1, Sheet1_2, Sheet1_3. Names are compared without regard to capitals, and kept within Excel's 31 characters. Nothing is overwritten.

Formulas that refer to another sheet in the same file are updated if that sheet was renamed. Results are not stored in the merged file: Excel works them out again when you open it. Workbook-wide names are dropped, so a formula that uses one will show an error. Formulas that refer to a sheet range across several sheets are not rewritten.

Charts, pictures and shapes are not copied. Workbook-wide names and document properties are dropped. The theme of the first file is used for all. Two tables with the same name in different files are refused rather than renamed.

Only .xlsx. Workbooks with macros, pivot tables, slicers, embedded objects, data connections or links to other workbooks are refused with the reason. If one file cannot be merged, nothing is merged. Password-protected and legacy .xls files are not supported.

Yes. Choose Single spreadsheet: the rows of every chosen sheet are put under each other in file order, columns matched by position, not by header text. Keep the first header only, every header or none; limit every sheet to a data range such as A1 to Z1000; drop empty rows. A sheet with a formula that refers to another sheet is refused here; use Multiple sheets for those.

Yes. It runs on a server rather than in your browser: up to 20 files, 25 MB each and 100 MB together, and very large sheets are refused with a reason.