How to Open an XLSX File

What is an XLSX file?

.xlsx is the default spreadsheet format used by Microsoft Excel since Excel 2007, replacing the older binary .xls format. Structurally, an .xlsx file is actually a ZIP archive containing a set of XML files — one describing the workbook's sheets, one holding all the shared text strings, one per worksheet with its cell data, plus styling and metadata files. This is the same "Office Open XML" structure used by .docx (Word) and .pptx (PowerPoint).

That ZIP-based structure is exactly what the tool on this page reads directly: it opens the ZIP, decompresses the relevant XML parts using your browser's built-in decompression, and parses the cell data — all without any external spreadsheet library.

How to open an XLSX file on Windows

1. Double-click the file — it opens in Microsoft Excel if installed.
2. No Excel? Install the free LibreOffice Calc from libreoffice.org, which opens .xlsx files with strong compatibility.
3. Alternatively, upload it to Google Sheets (sheets.google.com) for free, browser-based editing.

How to open an XLSX file on Mac

1. Double-click the file to open it in Microsoft Excel if installed.
2. Without Excel, Apple Numbers (pre-installed on most Macs) opens and converts .xlsx files automatically.
3. LibreOffice Calc is also a free, cross-platform option available for Mac.

How to open an XLSX file on Android & iPhone

Android: The free Microsoft Excel app or Google Sheets app both open .xlsx files directly from Downloads, email attachments, or cloud storage.

iPhone: Tapping a .xlsx attachment offers to open it in the Excel, Numbers or Google Sheets app if installed, or gives a basic Quick Look preview otherwise.

Open an XLSX file online for free (Excel for the web & Google Sheets)

If you don't have desktop Excel — on a Chromebook, a work PC without Office, or a borrowed computer — two free browser options keep the file as a real .xlsx:

• Excel for the web: sign in at office.com with a free Microsoft account, upload the file to OneDrive and click it. Formulas, multiple sheets, charts and most formatting work; macros and some advanced features don't.
• Google Sheets: upload the file to Google Drive and double-click it. It opens in Office compatibility mode with an .XLSX badge next to the name, and edits are saved back to the same .xlsx. Choose File > Save as Google Sheets only if you want a converted copy.

Both services store the file in your cloud account. For a confidential workbook you only need to read, the viewer at the top of this page shows every sheet without the file leaving your device.

XLSX vs XLS — what's the difference?

.xlsx is the modern format (Excel 2007+), an XML/ZIP-based structure that's more compact, more resistant to corruption, and easier for other software to read. .xls is the older binary format from Excel 97–2003, using a completely different internal structure. Modern Excel, LibreOffice and Google Sheets all open both, but a tool built specifically to parse XLSX's ZIP/XML structure — like the one on this page — can't read the older .xls binary format, since there's no shared structure between them at all.

Is it safe to open an XLSX file?

A plain .xlsx file itself can't contain macros — that's what the separate .xlsm extension is for, and Excel enforces the distinction. However, an .xlsx can still contain formulas that pull in external data or links, so treat one from an unknown source with the same caution as any other document: avoid enabling "Edit Content" or following embedded links you don't recognize. Viewing the raw cell data first, like the tool on this page does, is a safe way to check a file's contents without letting Excel evaluate any formulas.

Common XLSX file errors and how to fix them

"Excel cannot open the file because the file format or file extension is not valid"

Usually means the file is either corrupted, or was renamed to .xlsx from a different format without actually being converted. Try opening it with the tool on this page or another viewer to check what's actually inside; if it's genuinely corrupted, you'll need to get a fresh copy from the source.

File opens but shows "Protected View" or won't let you edit

Excel opens files downloaded from the internet or email in read-only Protected View by default as a safety measure. Click "Enable Editing" in the yellow bar at the top, but only if you trust the source.

Formulas show as text instead of calculating (e.g. "=SUM(A1:A5)")

Usually caused by the cell being formatted as Text before the formula was entered. Change the cell format to General or Number, then re-enter the formula.

How to repair a corrupted XLSX file (Open and Repair)

When Excel finds damage it often offers to fix the file itself, with a message like the one below. Click Yes, and Excel then lists what it repaired or removed. If the file won't open at all, force a repair from the Open dialog:

1. In Excel, go to File > Open > Browse and select the damaged workbook (don't double-click it).
2. Click the small arrow next to the Open button and choose Open and Repair…
3. Click Repair to recover as much as possible. If that fails, repeat and choose Extract Data, which recovers cell values (and optionally formulas) without the formatting.

If Open and Repair doesn't work

• Restore an earlier version: for files in OneDrive or SharePoint, use File > Info > Version History in Excel, or right-click the file on onedrive.com and choose Version history. For local files with File History or restore points enabled, right-click the file in File Explorer > Properties > Previous Versions.
• Try another program: LibreOffice Calc and Google Sheets use different file readers and sometimes open a workbook Excel rejects; save the result as a new .xlsx.
• Read the raw data: because an .xlsx is a ZIP of XML files, the viewer at the top of this page can often display cell values even when styles or charts inside the file are damaged. If it reports a missing ZIP signature, the file isn't a valid .xlsx at all (see the next section).
• Unsaved work after a crash: go to File > Info > Manage Workbook > Recover Unsaved Workbooks (also linked at the bottom of File > Open > Recent) to see AutoRecover copies.

"File format or extension is not valid" and other files Excel refuses to open

The full message reads: Excel cannot open the file 'name.xlsx' because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file. Excel checks what's inside the file, not just its name, so this means the contents aren't a real .xlsx workbook. Work out which case you have:

• The file is 0 KB or much smaller than expected: the download or copy didn't finish, or a sync app (OneDrive, Dropbox) left only a placeholder. Download it again or let the sync complete.
• It's really another format with a .xlsx name: open it in Notepad and look at the first characters. A real .xlsx starts with PK (it's a ZIP). Text beginning with <html or <table is a web page export, plain comma- or semicolon-separated lines are a CSV, and ÐÏ followed by unreadable characters is an old .xls file. Rename it to the matching extension (.html, .csv or .xls) and open it again.
• It's password-encrypted: an encrypted workbook also doesn't start with PK, so non-Excel tools (including the viewer on this page) report it as invalid. Excel, LibreOffice and Numbers will ask for the password instead (see below).
• It's genuinely corrupted: try Open and Repair, described above.

Protected View, blocked files and "Enable Editing"

Files from the internet or email open in Protected View: read-only, with a yellow bar at the top. Click Enable Editing only if you trust the source. If Excel instead says it can't open the file in Protected View, or shows a blank window, save the file to your PC, right-click it in File Explorer, choose Properties, tick Unblock at the bottom of the General tab, and click OK. Macro-enabled workbooks (.xlsm) downloaded from the internet additionally show a red Security Risk bar because Microsoft blocks their macros by default; that is a deliberate protection, so only unblock files you fully trust.

Password-protected XLSX files

Excel has two very different kinds of protection, and it matters which one you're facing:

• Password to open (encryption). Set with File > Info > Protect Workbook > Encrypt with Password. Excel asks for the password before showing anything, and the whole file is encrypted with strong AES encryption. Without the password there is no legitimate shortcut; ask the person who sent it. If you know it and want to remove it, open the file, go back to Encrypt with Password, clear the box and save.
• Sheet or workbook-structure protection. Set with Review > Protect Sheet or Protect Workbook. The file opens normally but cells can't be edited, or sheets can't be added or renamed, until you use Review > Unprotect Sheet. This only restricts editing: the values aren't encrypted, so the viewer on this page and other spreadsheet apps can still display them.

A third, milder prompt asks whether to open the file as read-only unless you need to make changes. That's the author's "Read-only recommended" setting: click No to open it normally for editing.

Related file extensions

Technical references

The .xlsx format is Office Open XML, standardized by Ecma International as ECMA-376 and also published as an ISO/IEC standard.

• ECMA-376 — Office Open XML File Formats — The formal specification behind the .xlsx (and .docx, .pptx) file format, published by Ecma International.

Frequently asked questions