Version Information

• WordPress: 4.6.1
• MultilingualPress: 2.4.7

Steps to Reproduce

1. Base site with language English
2. Additional site with language en-GB
3. Ensure priority for both languages to the same value (I'm using 2)
4. Only redirect from main site, not from other language
5. Browse to main site from chrome, firefox, and safari

What I Expected

With system/browser language set to US english, no redirect occurs. This is the case in Chrome and in Firefox.

What Happened Instead

In Safari only, redirect occurs to en-GB despite system language set to US English.

*Note that not setting equal priority will cause the higher priority site to always load in any browser, regardless of system language.

Overall expectation

The larger desired behavior here is that if a user comes to the site with US English, no redirection occurs. If they come to the site with en-GB, they are redirected to the en-GB site.

Browser Information (all current versions on OS X)

Here are the Accept-Language header values for various browsers with a US English configuration

Safari
[en-us] => 1

Firefox
[en-US] => 1
[en] => 0.5

Chrome
[en-US] => 1
[en] => 0.8