Free CISO to ISO Converter

Instant, private & offline-capable PSP CSO / CISO decompressor. Drag & drop your compressed game image and get a full, lossless ISO in seconds — no uploads, no ads, no tracking.

BROWSER ONLY · 0% UPLOAD

Select or Drop a CISO / CSO File

Max practical size depends on your RAM. For best performance keep < 2 GB in browser. Fully lossless.

About This CISO / CSO to ISO Converter

This lightweight, single‑file web app converts compressed PSP CISO / CSO images back into original, 100% lossless ISO files directly in your browser. Everything happens locally – your game image never leaves your device, protecting privacy and saving bandwidth. It uses an optimized JavaScript implementation of the CSO (CISO) format plus fast in‑browser zlib (pako) decompression. Designed to embed easily in WordPress (Kadence theme tested), forums, wikis, or emulator community sites without extra dependencies. The interface is responsive, mobile friendly, and intentionally distraction free so you can focus on quick, reliable conversion.

Compared with typical “online” converters that upload large files to remote servers, this tool delivers instant feedback, zero waiting queues, and superior security. Use it for restoring compressed backups, verifying integrity, or preparing images for patching. Bookmark it – it also works offline after your first load (served as static HTML). Enjoy fast, private, no‑cost conversions.

How to Use

Click or drag a .cso or .ciso file into the drop zone.
Press Convert to ISO. Watch the real‑time progress, speed, and block counter.
When finished, a download button appears. The file name is preserved; only the extension changes to .iso.
Verify the ISO in your emulator or hash tool if desired.

If you accidentally picked the wrong file, use Clear to reset quickly. You can cancel mid‑conversion; partial output is discarded safely.

Tips & Best Practices

Performance: Close unused tabs to free memory for large images (>1 GB).
Integrity: The process is deterministic; mismatched magic headers or corrupt blocks are reported instantly.
Speed: Modern browsers with hardware acceleration (Chromium, Firefox) decompress faster.
Offline: After first load it can run offline (static assets only).
Embedding: Paste this HTML into a Kadence theme Custom HTML block – styles are namespaced and won’t clash.
Limits: Extremely large CSO files may exceed available RAM; split or run via desktop tools if that happens.

Need the reverse (ISO to CSO) or batch mode? Save this page and extend the script – the structure is clean and commented.

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