Downgrading iPod OS to 4 from 5

Discussion in 'Misc' started by, Nov 5, 2011.

  1. Guest

    At my last syn, my iPod OS was upgraded to 5, but I find an app I use
    a lot (Wifitrak) now no longer works. It isn't particularly important
    to me to used the new facilities of iOS 5, so I want to go back to iOS
    4. How can I do that?
    , Nov 5, 2011
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  2. David Empson Guest

    This isn't a Mac question, but I'll answer it here anyway. For future
    reference, please use one of these groups for iOS questions, depending
    on the device type:

    For a non-jailbroken iOS device, you cannot downgrade to an older
    version of iOS. Apple's servers authenticate each iOS installation and
    don't permit older versions to be installed.

    If I remember right, Apple started doing this as of iOS 3.1.3, so in
    theory you might be able to manually downgrade to 3.1.2 or earlier, if
    your device is old enough to run that version and you kept a copy of the
    firmware image.

    For jailbroken devices, the procedure for downgrading requires you to
    have planned ahead and saved a special file when the previous OS version
    was installed, and have a copy of the previous firmware version. Even if
    you manage to install it, you might run into problems using the
    downgraded iOS version, because you can't downgrade the firmware in the
    baseband (communications) processor, so you will have a mixture of older
    main firmware with newer baseband firmware, and they may have
    compatibility issues.

    WiFiTrak and all similar apps broke with iOS 5 because they were using
    an undocumented internal programming interface ("private API") in
    previous versions of iOS to access more information from the WiFi
    hardware than is available through official programming interfaces
    supplied by Apple. Those apps were removed from the App Store some time
    during the life of iOS 3 (if I remember right), because the use of the
    private APIs was a violation of the developer agreement. They only kept
    working in iOS 4 because Apple didn't happen to change the private APIs
    relating to WiFi. Apple has changed those APIs in iOS 5, rendering all
    applications using those APIs unable to function.

    I also had WiFiTrak, but I didn't use it much so I just shrugged and
    deleted it from my devices when I found out it didn't work any more once
    my iPhone and iPad were running iOS 5.
    David Empson, Nov 6, 2011
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