This is something that occasionally comes up when talking to clients about Globalization/Localization planning. Here is a list of best practices based on research.
- Don’t use flags when the intent is to signal language.
- It’s ok to use flags to represent country/market but follow with the language.
- Always use the name of the language in its local format.
- Have a consistent place for the language/market selector across the site (header, footer).
Additional Articles for Reference