An XLSX file is a spreadsheet saved in Microsoft Excel's modern format

XLSX is the file format that Microsoft Excel uses to store spreadsheets. The X in XLSX stands for XML, which is the underlying code structure. When you save a spreadsheet in Excel 2007 or later, it saves as .xlsx by default. The file contains rows, columns, formulas, charts, and formatting — everything you see on screen gets packaged into that single file.

Before XLSX existed, Excel used the .xls format, which is older and less flexible. XLSX files are smaller, more secure, and work better with other programs. You will see XLSX files everywhere: budgets, schedules, inventory lists, financial reports, and data analysis.

The main thing to know is that XLSX is just a container. It holds data in a grid, and that data can be numbers, text, dates, or formulas that calculate results. You do not need to understand the XML code inside — the program that opens the file handles all of that for you.

Key Takeaways

  • XLSX files are spreadsheets created by Microsoft Excel 2007 and newer versions, containing rows, columns, and formulas in a single file.
  • You can open XLSX files with Microsoft Excel, Google Sheets, Apple Numbers, or free programs like LibreOffice Calc.
  • XLSX files are smaller and more secure than the older XLS format, and they work across different devices and operating systems.
  • If you receive an XLSX file but do not have Excel, you can still open and edit it using free web-based tools like Google Sheets.

How to open an XLSX file on Windows or Mac

If you have Microsoft Excel installed, opening an XLSX file is straightforward: double-click the file and it opens in Excel. On Windows, you can also right-click the file, select "Open with," and choose Excel from the list.

If you do not have Excel, you have free options. Google Sheets is the easiest: go to Google Drive, click "New," select "File upload," and choose your XLSX file. Google Sheets opens it in your browser and you can view and edit it there. On Mac, Apple Numbers is built in and opens XLSX files — just double-click and it launches in Numbers.

LibreOffice Calc is another free program that works on Windows and Mac. Download it from libreoffice.org, install it, and XLSX files will open in Calc by default. WPS Office is a third option that handles XLSX files well and is available for both systems.

Opening XLSX files on phones and tablets

On an iPhone or iPad, the easiest route is the Microsoft Excel app from the App Store. It is free and opens XLSX files directly. You can view, edit, and save changes back to the file.

Google Sheets also works on phones and tablets. Open your web browser, go to Google Drive, upload your XLSX file, and open it in Sheets. The mobile version is simpler than the desktop version but handles basic editing.

On Android, Microsoft Excel from the Google Play Store is the official option. Google Sheets works the same way as on iPhone — upload to Drive and open in the app. Both are free.

What happens when you convert XLSX to other formats

You can save an XLSX file as other formats depending on what you need. In Excel, go to File, then "Save As," and choose the format from the dropdown. Common options include CSV (comma-separated values, which is plain text), PDF (for printing or sharing without editing), and XLS (the older Excel format).

CSV is useful when you want to import data into another program or database. PDF is best when you want to send a file that looks exactly the same on every device and cannot be edited. XLS works with very old versions of Excel, but there is rarely a reason to use it now.

Google Sheets and LibreOffice Calc both have "Download as" options that let you save to different formats. The conversion usually works smoothly, though complex formulas or formatting might not transfer perfectly to simpler formats like CSV.

Why XLSX files sometimes will not open

The most common reason an XLSX file will not open is that you do not have a program installed that reads it. The solution is to download one of the free options listed above — Excel, Google Sheets, Numbers, or LibreOffice Calc.

Sometimes a file is corrupted, which means the data inside got damaged. This can happen if the file was not saved properly or was interrupted during download. If you have the original file from the sender, ask them to send it again. If you created the file yourself, you may have a backup or an earlier version saved on your computer.

Occasionally an XLSX file is password-protected, which means you need a password to open it. If you forgot the password, there is no built-in way to recover it — you would need to contact whoever created the file.

XLSX vs. other spreadsheet formats

XLSX is Microsoft's format, but other companies make spreadsheets too. Google Sheets saves as GSHEET by default, but can export to XLSX. Apple Numbers uses NUMBERS format but can also export to XLSX. LibreOffice Calc uses ODS format natively but works with XLSX.

The practical difference is small: XLSX is the most widely used, so if you are sharing a spreadsheet with someone and are not sure what they have, XLSX is the safest choice. Most modern programs can read and write XLSX files, even if it is not their native format.

CSV is simpler than XLSX — it is just plain text with commas separating columns. It has no formatting, no formulas, and no charts. Use CSV when you need to move raw data between programs. Use XLSX when you need to keep formulas, formatting, and structure intact.

Frequently Asked Questions

Can I open an XLSX file without downloading anything?

Yes. Go to Google Drive, upload your XLSX file, and open it with Google Sheets. You can view and edit it in your web browser without installing any software. Microsoft also offers Excel Online through Office.com if you have a Microsoft account.

Will my formulas and formatting stay the same if I open XLSX in a different program?

Usually, but not always. Google Sheets and LibreOffice Calc handle most Excel formulas correctly. Very complex formulas or advanced formatting might not transfer perfectly. If you are working with a complicated spreadsheet, test it in the other program first before relying on it.

What is the difference between XLSX and CSV?

XLSX is a formatted spreadsheet with formulas, charts, and multiple sheets. CSV is plain text with data separated by commas — no formatting or formulas. Use XLSX for spreadsheets you will edit and format. Use CSV to move raw data between programs.

Can I edit an XLSX file on my phone?

Yes. Download Microsoft Excel or use Google Sheets in your browser. Both let you view and edit XLSX files on phones and tablets. Changes save back to the file, so you can pick up where you left off on a computer.

Is XLSX the same as XLS?

No. XLS is the older Excel format from before 2007. XLSX is the newer format. XLSX files are smaller and more compatible with other programs. Most people use XLSX now, but some older systems still use XLS.