The PSP model that did not have a UMD drive was the PSP Go. Sony designed the PSP Go as a smaller, slide-screen version of the PlayStation Portable, and it replaced physical UMD games with digital downloads.
The PSP Go launched in 2009 with 16 GB of built-in flash storage, considerably changing how games and media were acquired. Users downloaded compatible software through the PlayStation Store or transferred it from a PlayStation 3 or a computer using Sony's Media Go software. Storage could be expanded with a Memory Stick Micro card.
The other listed models retained UMD support. The PSP-1000 and PSP-3000 used the original disc format, while the PSP Street, also known as the PSP-E1000, was a budget redesign that still included a UMD drive. Because it lacked a disc drive, the PSP Go could not use an owner's existing UMD collection, making it a digital-only PSP.