Getting several spreadsheets into one file is a common step before sending a report or archiving data — but doing it by hand, opening each file and copy-pasting sheets, is tedious. InstantTools Excel Merger uses the SheetJS engine to combine your files into a single workbook entirely in your browser, so nothing gets uploaded.
What "merge" actually means here
This tool combines files by stacking each source file's sheets as separate tabs inside one output workbook — it does not join rows together or align columns across files. If you upload sales_jan.xlsx and sales_feb.xlsx, the result is one .xlsx file containing both as separate tabs (renamed to stay unique and within Excel's 31-character sheet-name limit), not a single combined table of rows.
That makes it a good fit for consolidating multiple reports into one deliverable file — but it is not a row-level join or a "vertical append" tool. If you need to stack rows from files that share the same columns into one continuous table, or join two files on a shared key column, this tool doesn't do that today; you'd need to do that step in Excel/Sheets after downloading the merged file, or with a formula-based approach.
Why do this locally instead of uploading?
Most online "Excel joiners" require uploading your files to their servers, where sensitive business data can be exposed. Because the entire merge runs in your browser's memory via SheetJS, nothing leaves your device.
How to merge spreadsheets
- Drag and drop two or more
.xlsx,.xls, or.csvfiles into the uploader. - Click "Run & Download." The engine reads every sheet from every file and appends each one as its own tab in a new workbook.
- Download the resulting
.xlsxfile — every source sheet is preserved as a separate tab.
Common use cases
- Combine several regional or monthly report files into a single file to send or archive.
- Consolidate spreadsheets from different teammates into one workbook without manually copying tabs.
- Bundle a set of related CSV exports into one
.xlsxfile for easier handling.
Frequently Asked Questions
Does this combine rows from files with the same columns into one table?
No — each source file's sheet becomes its own tab in the output workbook. If you need the rows combined into a single continuous table, do that step afterward in Excel/Sheets, or use our Deduplicate Rows tool on the result if you're worried about duplicate entries.
Can I merge CSV files with Excel files?
Yes — .xlsx, .xls, and .csv are all accepted in the same upload.
Is the original formatting preserved?
Cell values and data types carry over. Complex formatting, macros, or advanced cell styling may not be preserved exactly, since the file is re-read and re-written by the SheetJS engine rather than copied byte-for-byte.
Does this tool send any data to a server?
No. The entire merge happens in your browser's memory using SheetJS. Nothing is uploaded.
Is there a limit on file size or number of files?
Free accounts can process files up to 100MB each. Premium accounts can handle files up to 500MB. Because everything runs in your browser's memory, very large combined workbooks are limited by your device's available RAM rather than a fixed row count.