Combine the sheets of an Excel file

The problem it solves

It is the most common file in the world: a workbook with twelve tabs, January, February, March… each holding the same table again. It is comfortable to fill in and impossible to analyse. No pivot table reads twelve sheets at once, and any yearly total ends up as a formula adding twelve cells across twelve tabs, which breaks the moment someone adds a sheet.

What you need is one continuous table with the rows from every sheet one after another. That is exactly what you download here.

The sheet-name column

When you flatten the workbook, the information held in the tab name — "this row is March" — disappears, because the tab no longer exists. That is why the "Add a column with the sheet name" option is on by default: it appends a column holding the name of the sheet each row came from. It is called Sheet by default, and you can rename it to something meaningful such as Month or Branch.

Without that column, a workbook organised by month becomes a pile of undated rows. With it, you have exactly the column to group by in a pivot table.

When the sheets do not share columns

They do not have to be identical. The columns in the result are the union of them all, in the order they first appear: if October's sheet has a Returns column the others lack, that column exists in the result and stays empty on the rows from the other months.

Matching is by column name, so Amount goes with Amount even if it sits in a different position on each sheet.

A workbook with only one sheet

If you upload a file with a single sheet there is nothing to combine, and the tool says so rather than handing you back a copy of your file. That usually means you uploaded the wrong file, or that the "tabs" you thought you had are in fact separate files — in which case what you want is Merge by stacking rows.