Prior to the [[iPod touch (4th generation)]] and up until the introduction of A4 series chipsets into the iPod lineup, Apple had yet to implement any restrictions to lock users away from flashing unsigned .IPSWs onto iPods using iTunes. On devices featuring the A4 chip, flashing unsigned .IPSW files had been restricted and would be impossible, meaning you would have to restore your device to the latest signed version provided by Apple and to seek recourse through jailbreaks and experimental workarounds. On devices preceding the A4, the [[iPod touch (3rd generation)]] and below, you may interchangably use unsigned .IPSW files according to the device. In this table, the .IPSWs you can no longer restore to are marked with [[File:Apple X.png|frameless|x20px|Unsigned by Apple]] and those of which you can restore from are prefixed either with [[File:Apple.png|frameless|x20px]], indicating it is unsigned but restorable and [[File:Apple checkmark.png|frameless|x20px|Signed by Apple]] indicates it still signed by Apple and restorable.