Considerations for Data Loader, special characters, file encoding, and import

This behavior is the result of a combination of your import file's encoding and the Data Loader settings you have selected and is not an unexpected issue with, or due to a change in, the Data Loader application.

When Configuring Data Loader you'll see the "Read all CSVs with UTF-8 encoding" setting. By checking this preference, you're forcing the application to attempt to render any CSV you choose for a data operation as if it has been saved with UTF-8 encoding despite whether the file may or may not be. The combination of enabling this setting and using a file that is not encoded in UTF-8 can result in ‌unexpected characters.

Although the Data Loader setting influences this behavior, the source of the issue is the way the file's encoding is set on saving the CSV file.  When using Microsoft Excel to save a CSV file, its encoding is automatically set using machine-specific ANSI encoding and not UTF-8.  It is not possible to explicitly configure or manually change this CSV file encoding behavior in Windows or Excel.  
 

To resolve the unexpected character import behavior, you have two options:

•  Leave the "Read all CSVs with UTF-8 encoding" setting enabled. If you commonly work with files containing special characters, this method is recommended to ensure all of the characters are captured properly. However, all CSV files used with the Data Loader need to be encoded using UTF-8.  You can use a text editor program such as Notepad to manually change the CSV's encoding to UTF-8 from ANSI so your import file is compatible with this Data Loader setting. To manually set file encoding, follow the instructions outlined in the documentation Why isn’t Data Loader importing special characters?

• Disable the "Read all CSVs with UTF-8 encoding" preference in the Data Loader. This will allow the default ANSI character encoding set by Excel to be passed without interference from the Data Loader.

Why have I never had to change this Data Loader setting or manually set file encoding until now?

It's likely that this is due to previously supplied files already being saved with UTF-8 encoding or they may not have contained special characters. Alternatively, the way Excel is setting file encoding on saving CSVs may have changed on your local machine.