Not directly related to API, but my colleague in France recently asked me about Japanese language support for BIM 360 Docs. I knew BIM 360 Docs supports Japanese since last year or so. I remember testing it at that time. Unfortunately, I have forgotten how I did that last year. I ended up spending a little time exploring it myself (once again) to make it work. So here it is, I decided to make a note of it this time. It might get handy for people who support in more than one language like myself.
First, the product documentation is here. According to the documentation, currently BIM 360 Docs web supports in the following languages: English, German, French, Spanish, Brazilian Portuguese, Chinese, and Japanese.