Language automatically detected - SEO issue?

[Sonya*]

Hi,

this is what I am investigating right now. We have two languages on our site. English is only used in ACP and (was) generally disabled for the users. We do not have any English content and English interface makes no sense for us.

Somedays we have experienced a sudden fall in Google organic search traffic. Nothing has changed on the website so far. Except one thing: a week before it happened, IPS support has investigated an issue on our site and enabled English for it. They did not disabled it after all and we have not noticed it. 

What has happened? I assume that Google visited our site and started to see it half-English half-non-English. Interface was automatically set to English, but the content is in other language. Does it make sense?

We have read a Google docs and have found out that Google does not recommend to use cookies to detect browser language. But instead uses different URLs for different languages:
https://support.google.com/webmasters/answer/6144055?hl=en
https://support.google.com/webmasters/answer/182192?hl=en

We have disabled English again and are waiting right now if this will improve the search results.

Sonya

[opentype]

12 minutes ago, Sonya* said:

Somedays we have experienced a sudden fall in Google organic search traffic.

When was that? Have you checked it against things like Google core updates. Those are usually much more likely the cause of sudden traffic changes. 

[Sonya*]

Yes, there war indeed a major update around the time. But not exactly at that time. From my previous experience, major updates change something on the date they have been released. Our changes are slightly delayed 

We are investigating right now and this "automatic detect language" guess is one of the guess we have. Especially why Google does not recommend to use cookies for the language versions.

[bfarber]

We don't actually use cookies - we use the HTTP "Accept-Languages" header. But that's neither here nor there.

I would be interested to hear any results you determine from this change. It seems strange this would result in an SEO problem on the surface, but I guess your theory is possible.