What is Excel?

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.

Who uses it

Finance, operations and anyone who received a file from finance or operations.

Reading Excel

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.

Writing Excel

You get a single sheet with a header row and column widths sized to the content. Values are written as text unless type inference is on, which keeps identifiers like 0044 or 007 intact.

What it can hold

Excel is a spreadsheet format. A cell holds a value, a type, a display format and possibly a formula, and the four are stored separately. A machine can read the table back out of it without guessing, which is what makes it safe to convert into and out of.

It keeps

Types. A number stays a number and a boolean stays a boolean, so whatever reads the file next does not have to guess from how a value looks.
The difference between empty and missing, which most table formats cannot express at all.
A line break inside a cell, which survives rather than ending the row.
Presentation - weight, alignment, colour and widths - alongside the values themselves.

It cannot express

Nesting. Cells are flat, so structured values have to be flattened into extra columns or written into one cell as text.
A partial read. The document has to be complete to mean anything, so a truncated file yields nothing and a large one has to be held in memory whole.

What it looks like

Example Excel

id,name,role,started,hours
007,Halima Yusuf,"Analyst, data",2024-03-15,38.5
012,"Jonah ""Jo"" Pryce",Engineer,2025-11-02,
104,Wei Chen,Manager,2023-06-30,40

Questions

Does converting to Excel keep my formulas?

No. A table has values, not formulas. If your source came from Excel in the first place, the formulas were already resolved to their results before they reached this page. Anything that was =SUM(A1:A10) arrives as the number it produced.

How do I open Excel files?

Any text editor will show you the contents. To read it as a table, paste it into the converter on this site and it appears in an editable grid. Nothing is uploaded.

Is Excel a good format for sharing data?

It depends who is receiving it. Finance, operations and anyone who received a file from finance or operations. If the recipient is outside that group, a plain CSV travels further than anything else.