What is the correct method for encoding an Excel file into base64 to be uploaded through an API?

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The correct method for encoding an Excel file into base64 to be uploaded through an API is as follows:

1. Open the Excel file that you want to encode in base64.
2. Click on the "File" tab and select "Save As".
3. In the "Save As" dialog box, select "Web Page (*.htm; *.html)" as the file type.
4. Choose a location to save the file and click the "Save" button.
5. Open the newly saved HTML file in a text editor.
6. Locate the data in the file that corresponds to the Excel file, which can usually be identified by the file extension ".xlsx".
7. Copy the data from the HTML file and paste it into an online base64 encoder, such as https://www.base64encode.org/.
8. Click the "Encode" button to generate the base64 encoded string.
9. Use the generated string in the API request as the value for the relevant file parameter.