It's funny because I have a client right now asking for some advice on how to design a localizable website that can guess default language and I'm realizing that no one has really solved this very well.
The first and most important step is to offer a very very big option up front and center for reverting to English.
This is an extremely annoying thing when traveling.
Either way, it must like rule 1 of UI design; even if you think you know better than your user does, let them override that choice when you get it wrong.
Or rather the solution I would like is rarely used, I have only found it on some Amazon sites, where you can freely choose the country-level localization (via the domain) and the language-level localization (via a menu) independently.
It was an happy day when I was able to browse the German Amazon in English.
Getting my money back from google is impossible, according to google. Since they could not offer a solution to the language issue, they told me 4 times to complain at apple and try to get my money back from them.
Again: that was not my issue at al. The time it took to dialog with google support was 10 times as expensive as the rent for the movie anyway. I wanted my expectations to be met, was told that it's impossible, so I adjusted my exceptions when being offered to buy / rent from YT to zero.
Really? How about “guessing” that the client’s language preferences are those expressed in the Accept-Language request header?