What Excel is
An Excel workbook is a zip archive of XML parts describing sheets, cells, formulas, styles and charts. The .xlsx extension is that format; .xls is the older binary one from before 2007.
Finance, operations and anyone who received a file from finance or operations.
What Textile is
Textile marks header cells with |_. and data cells with plain pipes.
Redmine, and older Rails applications.
What changes when you convert Excel to Textile
Only the first sheet is read, and cells are read as the text Excel displays rather than the number underneath. That matters for dates: a cell showing 15/03/2026 arrives as that string, not as a serial number you would then have to decode.
The header row is written with the |_. marker so it renders as a header.
What carries over from Excel to Textile
Excel records 4 things about a table that Textile has no way to hold.
Excel distinguishes a number from the text of a number; Textile does not, so every value arrives as text and has to be re-parsed by whatever reads it next.
An empty cell and a missing one are the same thing in Textile, so a null and an empty string in the Excel both come out blank and can no longer be told apart.
A line break inside a cell ends the row in Textile, so line breaks are replaced rather than carried through.
Textile marks its header cells differently from its data cells, so the first row is written with that marker.
Anything visual in the Excel - weight, alignment, colour, column widths - has no counterpart in Textile and is dropped. The values are what survives.