Software⏱️ 2 min read📅 2026-05-29

How to Fix: Error trying to upload MS Excel file from JS front end to Python Flask back

Learn how to fix: Error trying to upload MS Excel file from JS front end to Python Flask back end.

Quick Answer: Try checking your system settings or restarting.

Error trying to upload MS Excel file from JS front end to Python Flask back end can be caused by several factors. The most common causes include:

🛑 Root Causes of the Error

  • File type not supported by Flask.
  • Incorrect file encoding or MIME type.
  • Insufficient permissions to upload files on the server-side.

🚀 How to Resolve This Issue

Method 1: Using the `requests` Library

  1. Step 1: Install the `requests` library using pip: pip install requests
  2. Step 2: Modify your Flask route to accept file uploads and use the `requests` library to handle file uploads.
  3. Step 3: Ensure that the file type is supported by Flask and that the file encoding is correct.

Method 2: Using the `flask-uploader` Library

  1. Step 1: Install the `flask-uploader` library using pip: pip install flask-uploader
  2. Step 2: Modify your Flask route to use the `flask-uploader` library and configure it to handle file uploads.
  3. Step 3: Ensure that the file type is supported by Flask and that the file encoding is correct.

💡 Conclusion

By following these methods, you should be able to resolve the error trying to upload MS Excel files from your JS front end to your Python Flask back end.

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