Supported Language

All languages interpreted by GPT-3.5 and GPT-4

The official OpenAI blog has the following performance ratings.
This graph cannot be used for direct translation evaluation, but it does give an approximate trend.

Ref: OpenAI Research GPT-4 (opens in a new tab)

In fact, languages not shown in this graph can be translated as long as they are within the range of what the model is learned. However, translation accuracy depends on the training data, and the accuracy will be lower for languages with fewer speakers (less data).