XLSX to CSV Converter
Many times we receive files with the .xlsx extension, but they do not open correctly or are required in CSV format for uploading into systems, databases, or data analysis tools.
Table of Contents
This becomes a problem especially when:
- Excel is not installed
- The system only accepts CSV files
- Renaming
.xlsxto.csvdoes not work - You want a quick browser-based solution
In this article, I’ll show you a fully working HTML program that allows you to:
- Select an XLSX file
- Convert it into CSV
- Automatically download the CSV on click
- Without installing Excel or any software
Why XLSX Files Fail to Open as CSV
An .xlsx file is not a text file.
It is a compressed binary format, while .csv is a plain text format.
That’s why:
- Renaming
file.xlsxtofile.csvdoes not work - Some systems refuse to open or import the file
- Errors occur during uploads
The correct solution is to convert, not rename.
Solution: Browser-Based XLSX to CSV Converter
We can solve this problem using:
- HTML
- JavaScript
- SheetJS (XLSX library)
This method:
- Works in Chrome, Edge, Firefox
- Runs entirely in the browser
- Requires no backend
- Automatically downloads the CSV file
How the Program Works
- User selects an
.xlsxfile - JavaScript reads the file using
FileReader - SheetJS parses the Excel data
- The first worksheet is converted to CSV
- Browser automatically downloads the CSV file
How to Use This Tool
- Copy the code into Notepad
- Save as
xlsx_to_csv.html - Open the file in Chrome / Edge
- Click Choose File
- Select your
.xlsxfile - Click Convert & Download CSV
- ✅ CSV file will download automatically
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Important Notes
- Converts first sheet only
- Internet required once (to load library)
- Safe for offline data
- No file is uploaded anywhere
- Ideal for data import & analysis
Common Issues & Fixes
Problem: Nothing happens on click
Solution:
- Open HTML file in a browser (not Notepad)
- Make sure internet is available
Problem: CSV opens with strange characters
Solution:
- UTF-8 encoding is used (Excel compatible)
XLSX to CSV Converter using SheetJS
Conclusion
If you are facing issues where:
- XLSX files do not open
- Systems require CSV format
- Excel is unavailable
This simple HTML program provides a clean, reliable, and free solution.
Why does an XLSX file not open when renamed to CSV?
Because XLSX and CSV are different file formats.
XLSX is a binary Excel format, while CSV is a plain text file. Renaming the extension does not convert the file — it only changes the name.
Do I need Microsoft Excel to convert XLSX to CSV?
No.
This HTML tool works entirely in the browser and does not require Excel or any other software.
Does this tool upload my file to a server?
No.
All processing happens locally in your browser. Your file is never uploaded anywhere, making it safe for sensitive data
Which browsers are supported?
The tool works in all modern browsers, including:
Google Chrome
Microsoft Edge
Mozilla Firefox
Will the CSV file download automatically?
Yes.
Once you click “Convert & Download CSV”, the CSV file is generated and download starts automatically.
Which Excel sheet is converted to CSV?
Only the first worksheet in the Excel file is converted.
This keeps the process simple and avoids ambiguity.
Can this tool convert multiple sheets?
The current version converts one sheet only.
However, it can be easily extended to convert all sheets into separate CSV files.
Is an internet connection required?
Internet is required only once to load the conversion library.
After that, the tool works normally in the browser.
What if nothing happens when I click the convert button?
Check the following:
You selected a valid .xlsx file
The HTML file is opened in a browser, not in Notepad
Your internet connection is active