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Users who are particularly concerned about their device’s proneness to security vulnerabilities might want to update to iOS 11 anyway.
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Apple rarely - if ever - issues security-related updates for legacy versions of its software.
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Of course, the slight reduction in speed is offset by the new security patches that iOS 11 brings. On the other hand, the iPhone 5s will still get many of the new features in iOS 11 - including new app capabilities and UI changes, the revamped Control Center and built-in screen recording, Do Not Disturb While Driving, and the new Files app for managing files.
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Cold booting the phone also takes longer, about 12 seconds longer to be exact, according to ARS Technica’s testing. The native Maps app takes the biggest hit, with testing showing that it takes a full extra second to open in iOS 11 than in previous software versions. Safari, for example, will open in about 1.5 seconds in iOS 11, rather than 1.2 seconds on iOS 10.3.3. In many cases, apps will load up only marginally slower in iOS 11 than in iOS 10.3.3 for the iPhone 5s.
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