Locale-less URLs cause redirection to URL for ja/Japanese-localized article

In my Chrome or Firefox, when I open https://developer.mozilla.org/docs/Web/MathML/Element/mover or other locale-less URL, I get re-directed to https://developer.mozilla.org/ja/docs/Web/MathML/Element/mover (the ja-localized version of the doc).

And that’s in spite of the request not having an request headers that indicate a preference for Japanese:

Accept-Language: en-US,en;q=0.5 (in Firefox)
Accept-Language: en-US,en;q=0.9 (in Chrome)

So is the development server maybe doing some kind of content negotiation based on a reverse lookup of my IP address?

It’s interesting that I don’t see this behavior in Safari. In Safari I get redirected to https://developer.mozilla.org/en-US/docs/Web/MathML/Element/mover (en-US) as expected. Maybe that’s due to Safari having a simpler Accept-Language header?

Accept-Language: en-us (in Safari)

[sideshowbarker]

Could it be related to #128 - as in: do you have a cookie set to indicate Japanese preference?

Indeed yes, thanks — I find now that there was a preferredlocale cookie set to ja in both Chrome and Firefox. After deleting that cookie, I get redirected to the en-US article as expected

[Ryuno-Ki]

Could it be related to https://github.com/mdn/yari/issues/128 - as in: do you have a cookie set to indicate Japanese preference?