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Firefox is adding profiles to separate your browsing sessions
(www.theverge.com)
This is a most excellent place for technology news and articles.
containers are for general browsing; profiles are for the whole browser
profiles allow you to have different addons installed, different configurations between addons in different profiles, different browser settings (eg a SOCKS proxy for work profile, or a different default search engine, default fonts, etc… or for technical users you can have a profile with experimental settings turned on)