A technical centric view of a browser would focus on the rendering engine. But modern browsers, in their being almost small operating systems, go very far beyond the HTML&#x2F;CSS&#x2F;JavaScript rendering engine. I will list a few things that vary between browsers irrespective of the rendering engine: tab handling, incognito mode, extension system&#x2F;ecosystem, privacy handling, search&#x2F;url bar&#x2F;completion, security policies, anti malware strategies, download manager, history management, bookmark management, cross platform syncing, password management. And all these things have a higher impact on the user experience than the rendering engine.<p>All these things might be completely different between Firefox and Safari on iOS. Saying that Firefox on iOS is not &quot;a real browser&quot; is an understatement.