Options: Game Language

The Game language option lets you specify which language you're running Hearthstone in.

This setting only affects how the Deck Overlay detects cards played. The HearthStats Uploader will monitor your game correct no matter what language you're using, because it uses pixel detection detect your game — the pixels don't change for different languages. However when you are using Screen Analysis + Log Monitoring with the Deck Overlay then HearthStats Uploader will detect cards played by their name, and these card names change depending on which language you've selected in Hearthstone. If you're not playing in English then you will need to change this setting for card detection to work.