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What is an XLSX file?
The Excel XLSX format explained: what it stands for, what's inside, how to open one without Excel, and how it compares with XLS, XLSM and CSV.
An XLSX file is a Microsoft Excel workbook. It's the standard file format Excel has used since 2007, so if someone emails you a spreadsheet today, it's almost certainly an .xlsx file. It can hold several sheets, plus formatting, formulas, charts, images and filters.
What XLSX stands for
XLS comes from "Excel spreadsheet", the name of Excel's original file type (.xls). The X added in 2007 stands for XML: the new format is built on Office Open XML, an open standard (ECMA-376, ISO/IEC 29500). Under the hood, an .xlsx file is actually a zip archive full of small XML files, one for each sheet plus files for styles, shared text and settings. Rename one to .zip and you can look inside.
How to open an XLSX file
Step-by-step help for every device is in how to open an XLSX file. In short:
- Microsoft Excel on Windows or Mac, or the free Excel for the web with a Microsoft account.
- Google Sheets: upload the file to Google Drive and open it with Sheets.
- Apple Numbers on Mac, iPhone and iPad opens .xlsx files directly.
- LibreOffice Calc: free and available for Windows, Mac and Linux.
- In your browser, no install: drop it into our XLSX viewer. The file isn't uploaded.
XLS vs XLSX vs XLSM and other Excel file extensions
| Extension | What it is | Used since |
|---|---|---|
| .xlsx | Standard Excel workbook (Office Open XML). Up to 1,048,576 rows × 16,384 columns per sheet. | Excel 2007 |
| .xlsm | Same as .xlsx, but can contain macros (VBA code) | Excel 2007 |
| .xlsb | Binary workbook: faster and smaller for huge files | Excel 2007 |
| .xls | Old binary format, limited to 65,536 rows | Excel 97–2003 |
| .xltx / .xltm | Templates (without / with macros) | Excel 2007 |
| .csv | Plain text, one table, no formatting. See what is a CSV file | Any program |
XLSX vs CSV
An XLSX file keeps everything: multiple sheets, formatting, formulas and charts. A CSV keeps only the values from one table, but nearly every program can read it, which is why databases, online stores and email tools usually ask for CSV. The full comparison is in XLSX vs CSV.
How to convert an XLSX file
- To CSV: Excel's File › Save As › CSV UTF-8 saves the sheet you're on. Our XLSX to CSV converter does every sheet at once, in your browser.
- From CSV back to XLSX: use the CSV to Excel converter, which keeps leading zeros and accents.
- From an old .xls: open it in Excel and choose File › Save As › Excel Workbook (.xlsx), or convert it with our XLS to CSV converter.
- From JSON: JSON to Excel.
Are XLSX files safe?
Plain .xlsx files can't contain macros, so they're safer than .xlsm or old .xls files, which can carry VBA code. Still, only open spreadsheets from people you trust, and if Excel shows a yellow "Enable Content" bar on a file you didn't expect, don't click it.
FAQ
Questions
What is an XLSX file?
An XLSX file is a Microsoft Excel workbook saved in the Office Open XML format, the default format since Excel 2007. It can hold several sheets, formatting, formulas, charts and images.
What does XLSX stand for?
XLS stands for Excel spreadsheet (from the older .xls format), and the X at the end means the file is based on XML, the Office Open XML standard.
What program opens .xlsx files?
Microsoft Excel (Windows and Mac), the free Excel for the web, Google Sheets, LibreOffice Calc and Apple Numbers all open .xlsx files. To just look at one without installing anything, use our online XLSX viewer.
What is the difference between XLS and XLSX?
XLS is the older binary format used by Excel 97–2003. XLSX, introduced with Excel 2007, is a zipped set of XML files: smaller, more robust, and able to hold over a million rows instead of 65,536.
What is the difference between XLSX and XLSM?
They're the same format, except XLSM files can contain macros (VBA code). XLSX files can't, which makes them safer to open from unknown senders.
How do I convert an XLSX file to CSV?
In Excel, use File › Save As › CSV UTF-8, which saves the current sheet. To convert every sheet at once without uploading the file, use our XLSX to CSV converter.