Convert APK to CSO

A PSP or PSP emulator that requires a .cso image cannot install an Android .apk file. The required source is the matching PSP ISO, which can then be compressed to CSO for smaller storage.

What the APK format is

APK is the Android application package used to install software on phones, tablets, Android TV devices, and Android emulators. Android Studio, Gradle-based build systems, app stores, and backup tools produce or distribute APK files.

An APK is a ZIP-based package containing compiled Android code, resources, an AndroidManifest.xml file, signing certificates, and sometimes native libraries. Android interprets these components; PSP firmware and PSP ISO-loading software do not.

What the CSO format is

CSO, also called CISO, is a compressed PSP ISO disc image. It retains the disc-image structure expected by compatible PSP software while compressing its data blocks, reducing storage use and often reducing memory-card or disk requirements.

CSO support depends on the PSP custom-firmware loader, device, or emulator. Compression settings can affect loading speed, and some older hardware or software is more reliable with the original ISO.

Why direct conversion does not work

There is no valid APK-to-CSO conversion. Renaming app.apk to app.cso, opening the APK in an ISO utility, or compressing the APK with a CSO tool changes the filename or byte packaging but does not create a PSP disc image.

An Android port is different software from a PSP release. It cannot be made into the PSP version by changing its container, and CSO conversion does not translate Android code, remove encryption, change a game region, or make an Android application installable on a PSP.

How to create a CSO from a PSP ISO

1. Obtain the corresponding PSP ISO from your own disc or another authorized source. An APK usually does not contain this image.
2. If the source is an archive such as .zip, .7z, or .rar, extract it with a tool such as 7-Zip. The conversion input should be a valid file such as game.iso, not the archive.
3. Install maxcso, a current command-line ISO-to-CSO compressor for Windows, macOS, and Linux.
4. Run maxcso game.iso -o game.cso. Use the actual input and output paths if the files are in different folders.
5. Copy game.cso to the PSP emulator's ISO directory or to the location required by the PSP's custom-firmware loader.
6. Test the image and keep the original ISO until the game works correctly. The ISO is the compatibility fallback if the CSO loads slowly or fails.

For a graphical Windows workflow, UMDGen can open a PSP ISO and, in versions that expose CSO output, use File → Save As to save it as .cso. Verify the output in the target emulator because UMDGen versions and CSO support vary. maxcso is preferable for repeatable conversions, scripted jobs, and large files.

What to do if the APK contains an image

Some Android emulator packages or game front ends may bundle an image or game data inside assets/ or another directory. Extract the APK as a ZIP and inspect those files, but convert only an actual PSP-compatible ISO; Android resources, ROMs for another console, and emulator data cannot be used as PSP CSO input.

Online converters and compatibility limits

No reputable online converter can turn Android application code into a PSP disc image. Generic file-conversion websites may rename or recompress data, but they cannot supply the missing PSP executable and disc structure. Uploading APKs or game images also creates unnecessary privacy, copyright, and file-size risks, so use local tools for this conversion.

Use moderate CSO compression when loading performance matters, and select ISO output when the target device has unreliable CSO support. The source and destination must represent the same PSP software; compression changes storage format, not platform compatibility.