Whether or not an IPSW firmware file is signed determines whether or not you can use that IPSW to update iOS or whether or not you can downgrade iOS to a prior version. Put simply, if an IPSW firmware file is not being signed by Apple through their servers, it can not be used to place onto an iPhone, iPad, or iPod touch.
This leads to a fairly obvious question; how do you know if a particular IPSW iOS version is being signed by Apple or not?
By far the easiest way to check if an IPSW file is being signed is to check with a website like iNeal TSS (and yes you can do it yourself through Terminal but it’s a cumbersome process beyond what most users are interested in engaging with when just looking at a website gives you the same answer).
How to Check IPSW Firmware Signing Status
Here’s what you’ll want to do:
- First you’ll want to identify the iPhone, iPad, iPod touch, or Apple TV, get the identifier product ID for the device so that you can check it against the list
- Head to the iNeal API TSS site or ipsw.me (these are both unofficial sites) and locate the device you are looking to check IPSW signing status for*
- Now find the build number or iOS version release that coincides with what you wish to check, if the “signing” column says “YES” and is in green you can still use the IPSW, if it says “NO” it is no longer being signed and is unusable
- If the IPSW is being signed, find a download link for the firmware in question so that you can use it, we typically post IPSW download links and link them here as they become available for each new iOS release
Pretty straight forward, right?
It’s important to remember that using IPSW files is considered advanced, and the vast majority of iPhone and iPad users are better off updating their devices from iTunes or with the Software Update option in Settings app.
Attempting to use the wrong IPSW for a mismatched device will not work, and obviously neither will using an IPSW file that is no longer signed by Apple.
Thus, if you ever decide to go this route, check to make sure the IPSW is being signed, and check to make sure you are getting the proper firmware file for the device you intend to use.
* Third party sites that check IPSW signing status may change over time. Apple does not currently provide official firmware signing information, thus why third party sites are used for this purpose instead.