Today was Apple's annual shareholders' meeting, which they hold at their headquarters over at 1 Infinite Loop (with overflow seating in Building 4). During the Q&A portion of the meeting, one member of the audience raised a question about the performance of iOS on older devices, pointing out that some users want to downgrade. Apple's Senior Vice President of Software, Craig Federighi, responded. He explained that they do not provide a way to downgrade largely because each iOS update improves the security of your iPhone, iPad or iPod touch. To downgrade iOS means that your device would be less secure, and easier for hackers to get into. iOS has always been tight on security and is the most secure mobile OS by a wide margin, but every once in a while, a vulnerability is discovered that Apple addresses through an iOS update. We usually recommend that users update to the latest version of iOS compatible with their device right away.

From the technical aspect, the reason that you cannot downgrade iOS is because Apple stops "signing" an iOS release a week or so after a newer release is made available. iTunes will only install iOS versions that Apple has signed, in other words, authenticated. If a user tries to install an older version, they may see an error from iTunes stating that "this device isn't eligible for the requested build."

Here's the thing... if the security risks are not enough to deter you from the desire to downgrade, then it may be good to point out that downgrading is often not a viable solution. When a problem crops up after doing an iOS update, some users immediately turn to trying to downgrade. Sometimes it's because something stopped working after the update, or sometimes it's because users notice battery or performance issues, and believe that the update is responsible. When users perform an update, iTunes does some checks on the hardware and software of your device. If you see an error message during or after upgrading, it could be an issue that has been lingering for a while, but was not detected until you tried to update. It isn't necessarily caused by the update itself. For example, Error 1 or -1: this usually indicates a hardware issue with the device. Users sometimes think the update is responsible, but it is really because of a routine check the system does when performing any iOS update. For performance issues, there are many standard troubleshooting steps such as closing running apps to improve performance. Such issues after an update are often coincidental, and can be solved by the standard troubleshooting.

Some users also wonder why their older device cannot run the latest version of iOS. For example, many 4th generation iPod touch owners wanted to know why their iPods were not compatible with iOS 7 or later. The reason is that it simply wouldn't run well. For users who complain that their older devices became slower after an iOS update, just imagine how slow it would be on an even older device that wasn't compatible. When Apple introduced iOS 9 last Fall, there was a big focus on performance, and it was the first major iOS update in history to support all of the same devices that the previous version supported.