Apple periodically stops signing the old versions of the operating systems that give life to our devices. Therefore, on occasion we can need to consult the list of versions that are still signed from Apple’s servers, the previous step to download them in IPSW format and install them on our devices.
IPSW, updates, betas and signatures
Apple servers sign more than the latest available version of operating systems. Consider, for example, that certain devices remain in previous versions like iOS 12 or even iOS 9. At the same time, Apple does not stop signing the previous version as soon as the update is released, but usually leaves a margin of time to check that everything is in order in the newer version before leaving the old one.
For all these circumstances, keeping track of which versions are being signed at all times requires that we go to a specialized website. Many of them communicate with Apple’s signature servers to update status and reflect it publicly. One of these websites is ipsw.me, which is the one we will refer to in this article.
Before we continue, however, let’s talk for a moment about the IPSW files that give the site its name. Currently we are all used to our devices updating from themselves, but a few years ago we had to turn to iTunes for the task. Now iTunes has been replaced by the Finder, but the system of downloading an update on our Mac and then installing it on the iPhone or iPad is still valid.
The format of these updates is precisely .ipsw, a file that contains the entire operating system and what is necessary to install it. Everything, except the signatures that Apple manages from its servers. So why would we want to install an update using an IPSW file? For various reasons, one is for install a beta which is not yet available publicly, the other is to install a version older than the one we currently have running on the device. In the latter case, we will need the Apple servers to continue authorizing the installation.
How to download an IPSW and check if Apple is still signing
Having seen the concepts, let’s see how to check what versions continues to sign Apple on its servers and how to download the IPSW corresponding. In ipsw.me the process is joint, so here we will also explain it like this. The steps are the following:
- We enter ipsw.me.
- We choose the device whose IPSW interests us.
- We choose the exact model of the device.
- We choose the IPSW that we want to download, noting that if it is in red, Apple has already stopped signing it.
- We hit the button Download.
In step three it is important that we choose our device correctly, since the IPSW is unique for each of them and it cannot be exchanged. There would be no error if we downloaded the wrong one, the system would simply alert us to it and we would have to download the correct one again.
When the download is finished we can use Finder to install this update. We simply connect our device to the Mac and in the Finder information tab we touch the button To update while we hold down the Option (⌥) key, this will allow us to choose, from our files, the IPSW that we want to use for the installation.