Excel editor
Open, edit and format .xlsx spreadsheets right in your browser — styles, merges and formulas preserved, saved back as a real Excel file. Fully offline.
Open Excel editor →What is the Excel editor?
A free, fully offline spreadsheet editor that lands you straight in a ready-to-use workbook and opens .xlsx workbooks (and CSV files) right in your browser. Edit cell values, apply formatting — bold, colours, alignment, number formats — merge cells, freeze panes, resize and insert rows or columns, and manage multiple sheets, then save the result back as a real styled .xlsx file. It runs on Caspian Office's own built-in spreadsheet engine: nothing is uploaded, no account is needed, and it works without an internet connection. Your original file is never modified — saving always downloads a fresh copy.
How to use Excel editor
- Start straight away — The editor opens directly into a ready-to-use blank workbook (or your autosaved session). To edit an existing file, press Open, use Ctrl+O, or drop an .xlsx or .csv onto the grid — everything stays on your device.
- Edit cells in the grid — Click a cell and type, or press F2 to edit in place. The formula bar shows the underlying value or formula, and the name box jumps to any cell reference.
- Format your data — Use the toolbar for bold, italic, underline, font size, text and fill colours, alignment, text wrap and number formats such as percent, currency and dates.
- Arrange the sheet — Insert or delete rows and columns, drag header edges to resize them, merge cells, freeze panes at the active cell, and add, rename, reorder or delete sheets from the tab strip.
- Save your work — Download the workbook as a styled .xlsx file, or export the active sheet as CSV. Work in progress is also autosaved in your browser so you can restore it later.
Frequently asked questions
Are my spreadsheets uploaded anywhere?
No. The editor opens, edits and saves everything in your browser using Caspian Office's own spreadsheet engine, so your data never leaves your device. It also works fully offline.
Do formulas recalculate while I edit?
Not yet. Formulas are preserved and their last calculated results are shown, but this version does not recalculate them when you change other cells. Saved files are marked so Excel or LibreOffice recalculates everything the moment they are opened. Live recalculation is planned for a future release.
What happens to charts, images and pivot tables?
They are not supported yet. If a file contains them you will see a warning when it opens, and they will not be included in the copy you save. Your original file is never touched, so nothing is lost from it.
Can I open legacy .xls files?
No — the editor reads modern .xlsx workbooks and CSV files. For an old .xls file, use the Excel converter tool or re-save it as .xlsx first.
Is my work saved if I close the tab?
The working document is autosaved in your browser's local storage every few seconds. When you return to the tool it offers to restore the last session. This is a convenience copy — for anything important, download the .xlsx file.
How large a spreadsheet can it handle?
The grid is virtualised, so scrolling stays smooth even with tens of thousands of filled cells. Very large files simply take a few moments to open and are best saved back to .xlsx rather than CSV.
Tips
- Press Ctrl+B, Ctrl+I or Ctrl+U to format the selection, Ctrl+Z / Ctrl+Y to undo and redo, and Ctrl+S to download the .xlsx.
- Type a value ending in % (like 25%) or a date (like 2026-07-18) and the right number format is applied automatically.
- Copy and paste works with other apps too — pasted tab-separated text from Excel or a web page fills the grid from the active cell.
- Use Ctrl+arrow keys to jump to the edges of a data region, just like in Excel.
- Freeze panes keeps header rows visible while you scroll: select the first cell below and right of what should stay fixed, then press Freeze.