This article documents an issue where Liferay Digital Experience Platform (DXP) 7.0 stores the locale (e.g. /fr) of a guest session (that is, no one has signed in yet) and then keeps the same locale even after a user has signed in (authenticated). Users might still see /fr in the URL even if they are English (or Japanese, or Spanish) users.
The root issue is that Liferay DXP 7.0 stores information in a cookie called GUEST_LANGUAGE_ID.
Resolution
To resolve this issue, delete the cookie in the browser settings. Going to a URL with the desired locale will also change the cookie to that locale.
For example, if someone goes to localhost:8080/fr, the cookie will default to French as the preferred locale for guests on that machine. Either delete the cookie, or go to localhost:8080/en. This will change the cookie to have a default language of English.
Additional Information
Note: System administrators always have the option to enable only the locales they want using the locales.enabled= property in the portal-ext.properties file.