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<span itemprop="creator" itemscope="" itemtype="https://schema.org/Organization"><span itemprop="name" content="Outlook Mobile for iOS"></span></span>
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<div class="gmail_quote">What happens when users do that? Because they do.</div>
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A variety of kinda-horrible things will happen.</div>
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<div class="gmail_quote" style="direction: ltr;">The two copied profiles will compete for the Sync client record. That means sent tabs will appear on one or the other, the Tabs from Other Devices list will flip-flop between each of the two devices, the count
of devices will be wrong for scheduling purposes, and the two devices will unpredictably handle bookmark repair requests, leading to distributed inconsistency.</div>
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<div class="gmail_quote" style="direction: ltr;">If the two profiles are used on different versions, the browser metadata in the client record will flip between the two, too.</div>
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<div class="gmail_quote" style="direction: ltr;">Firefoxen that track who-did-what (e.g., on iOS we record whether a visit occurred locally or remotely) will
<i>both</i> think they did the thing for all historical data.</div>
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<div class="gmail_quote" style="direction: ltr;">From an FxA perspective I'm less sure: for a while (perhaps a long while) I expect they'll pretend to be the same device wrt FxA. Only one will show up in your devices list.</div>
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<div class="gmail_quote" style="direction: ltr;">We used to have the same problems with FHR, and perhaps telemetry, too.</div>
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