Picture of How to compress a .ISO to a .CSO (PSP game)
This instructable will teach you how to compress an .iso file to a .cso file. Using .cso files saves space on your PSP. This can only be done if you are running custom firmware.

This is only for backups of a PSP game you OWN and not DOWNLOADED.
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Step 1: Obtain a .ISO

Picture of Obtain a .ISO
To obtain a rip the umd of the game you own and then archive it as a .iso. I suggest using Active ISO File Manager 2. This can be downloaded for free at.


Here is a tutorial that I wrote that will help you better understand how to use Active ISO File Manger 2

I am using a copy of Star Wars Battlefront 2. (That I own)

Step 2: Download PSP ISO Compresser v1.4

Picture of Download PSP ISO Compresser v1.4
PSP ISO Compresser v1.4 can be downloaded for free at


Step 3: Convert

Picture of Convert
Select 'Compress ISO->CSO' on PSP ISO Compresser v1.4. Now input the location of your .iso and press compress.

Step 4: Now Play!

Picture of Now Play!
Just place the .cso into your ISO folder in your PSP. Now go to the game selection on your PSP and play it.

dmenezes3 years ago
can i convert a iso file to gba file..please let me know
Steamdnt6 years ago
I already posted this, A long time ago
you may have done a instructable on the same subject but the software is different and has a lot more options and easier to use
flamtz6 years ago
Good tutorial, now I know how to download those... oh wait did I just say that? No... what I mean is how big are the cso's?
Ikotoo (author)  flamtz6 years ago
Thanks. The size of the .cso depends on the game but .cso are always smaller then the .iso that you compressed it from. Usually They decrease in size by about 15-30%. cheers.