I believe that TMDb still uses the ISO 639-1 set of language codes. If it's not in that set it isn't supported.

If it's not in that set it isn't supported.

Wikipedia says that it is

I saw recently that a user was able to add a new language using the + sign. But I don't know if this is the right way to create a new website translation. Travis, would you mind enlightening us?

@JakubFabijan said:

Wikipedia says that it is

Indeed it is.

I saw recently that a user was able to add a new language using the + sign.

I tried it and got notification "Locale added successfully". Language was added and translating works, so I guess it is the right way.

@JakubFabijan said:

I want to help to translate TMDB to Esperanto, but it's not on the language list.

I also work on the *Esperanto * version/translation of TMDB