XLSX file format
XLSX is the Excel workbook format since Office 2007: formulas, charts and pivot tables in a compressed XML package that any modern spreadsheet app can open.
or drag & drop them here · images, video, audio and documents · up to 2 GB
What is XLSX?
Like DOCX, XLSX is Office Open XML in a ZIP wrapper — a folder of XML files describing sheets, shared strings, styles and formulas. The move away from the binary XLS format lifted its hard limits dramatically: a worksheet now holds 1,048,576 rows and 16,384 columns, against 65,536 rows and 256 columns before.
What XLSX stores is a live model, not just numbers. Formulas keep their references, charts stay linked to their source ranges, pivot tables remember their cached data, and conditional formatting travels with the sheet. That is precisely what CSV throws away, which is why exporting to CSV is a one-way trip for anything but raw values.
The tradeoff is weight and speed. Volatile formulas, whole-column references and thousands of conditional formatting rules make a workbook slow long before the row limit becomes an issue. For pure data interchange between systems, CSV remains the lighter choice; XLSX earns its place when the calculations and presentation matter.
| Extension | .xlsx |
|---|---|
| Category | Document |
| MIME type | application/vnd.openxmlformats-officedocument.spreadsheetml.sheet |
| Released | 2007 |
| Developed by | Microsoft |
| Compression | Lossless |
XLSX: frequently asked questions
- How many rows can an XLSX file hold?
- A single worksheet holds 1,048,576 rows and 16,384 columns. That is a sixteenfold increase over the old XLS limit of 65,536 rows. In practice, workbooks become painfully slow well before you approach the ceiling, so large datasets belong in a database.
- Why is my XLSX file so large and slow?
- Usually formatting rather than data: entire columns styled instead of the used range, thousands of conditional formatting rules, or embedded images. Volatile formulas that recalculate on every change are the other common cause. Cleaning up unused ranges often shrinks a workbook dramatically.
- XLSX or CSV for exchanging data?
- CSV when another system will import raw values — it is smaller, simpler and universally parseable. XLSX when formulas, multiple sheets, number formats or charts need to survive the trip. Exporting XLSX to CSV keeps only the values of the active sheet.
- Can I open XLSX without Microsoft Excel?
- Yes. Google Sheets, LibreOffice Calc, Apple Numbers and most online viewers read XLSX, including formulas and charts. Very advanced features such as Power Query steps, some pivot options and VBA macros are where compatibility starts to fray.
- Is XLSX really a ZIP archive?
- It is. Rename a copy to .zip and you can browse the XML for each sheet, the shared string table and the styles. This is how recovery tools rescue data from a workbook Excel refuses to open, and how scripts read spreadsheets without Excel installed.
- Do macros work in XLSX?
- No. XLSX deliberately cannot contain macros; a workbook with VBA must be saved as XLSM. That split is a security feature — it makes it obvious from the extension alone whether a spreadsheet is capable of executing code.