Highest Official Firmware for PSP: 6.61 (2015) - CFW Options for Homebrew

The last official Sony firmware for PSP is 6.61 (released 2015).

Custom Firmware (CFW) like 6.61 PRO-C2 or 6.61 Infinity adds homebrew, ISO loading, plugins, and perma-patch. CFW installation:

• Voids warranty (irrelevant now).
• Risk of brick if done incorrectly.
• Requires compatible model (1000, 2000 non-TA088v3, 3000, Go, Street).

For most users, 6.61 OFW + signed homebrew (via HEN) is safer. CFW for enthusiasts only.