Open · .xlsx
Open an XLSX File Without Excel
Someone sent you an .xlsx spreadsheet but you do not have Excel — or you would rather not pay for 365? Open it in your browser and keep the formulas intact. Nothing to install, nothing uploaded.
XLSX is the Microsoft Excel format. This editor opens it with the OnlyOffice engine, so cell formulas, number formats, colours and multiple sheets all survive — it is a real spreadsheet, not a read-only table. It runs locally with WebAssembly, so the file stays on your device.
The OnlyOffice spreadsheet engine is compiled to WebAssembly and runs inside your browser tab. Your file is read straight from disk into memory — there is no upload and no server — so private data never leaves your device. Because it is a live calculation engine and not a static preview, formulas recalculate as you edit. It reads the modern .xlsx format as well as older .xls and plain .csv, and can export back to XLSX or CSV.
How it works
- Click Open your XLSX to launch the editor in your browser.
- Pick an .xlsx file from your device, or drag and drop it onto the page.
- It opens with the OnlyOffice engine — view it, or edit cells and watch formulas recalculate.
- Download it again as XLSX or CSV when you are done.
What you can do
- Open any .xlsx (and .xls, .csv) file with formulas preserved
- Edit cells, then download again as XLSX or CSV
- No Microsoft Excel and no 365 subscription
- No upload — your spreadsheet never leaves your device
- Works offline as an installable app
It is just as good for a quick read-only look as for real work: sort a column, fix a figure, add a row or a formula, then hand the file back in the same format. This is handy when someone emails you a budget or a data export and you do not want to install Excel, pay for 365, or trust a random web converter with numbers you would rather keep private.
Frequently asked questions
Can I open an XLSX file without Excel?
Yes. It opens XLSX directly in your browser — no Excel or 365 subscription needed.
Are formulas and formatting kept?
Yes. The OnlyOffice engine preserves formulas, number formats and styling.
Is my spreadsheet uploaded?
No. It runs locally with WebAssembly and never leaves your device.
Can I export it to CSV?
Yes. Open it and download again as XLSX or CSV.
Does it work with old .xls files?
Yes. It opens .xlsx, older .xls and plain .csv files with the same engine.
Do my formulas recalculate?
Yes. It is a real spreadsheet engine, so formulas recalculate as you edit — not a static snapshot.
Are workbooks with multiple sheets supported?
Yes. Workbooks with several tabs open with all their sheets intact.