You may use Loader to import and update data using only CSV files. And it would not allow you to upload spreadsheet files such as Excel or Numbers, since it is critical that spreadsheet formatting does not impact data quality during import. Converting your spreadsheets to CSV files should not take too much time. Please check out our extensive CSV Guide on how to work with these files.
Loader supports CSV files with all of the most widely used delimiters. It's worth noting that the popularity of delimiters varies by region. Some countries use commas, whereas others use semi-colons. You are welcome to read our extensive CSV Guide, which covers everything about CSV files.
To learn more about delimiters please go to our CSV Guide and read What is a CSV delimiter?
Loader supports all major encodings. When you upload your CSV file, you will get a preview of how your data looks before you proceed with your import setup.