(unofficial firmware). This includes all "fat" and "slim" 20xx and 21xx models. Slim 25xx models may be exploitable, but only if their date code is 0D or less; sometimes date code 1A consoles may be on factory installed 3.55, however this should not be relied on. Slim 30xx and all "super slim" models cannot be exploited. These guidelines assume a console has not been taken to Sony to be serviced, as Sony may update the factory installed firmware. Custom firmware can be flashed using either a modchip or a WebKit exploit, which patches the current firmware and forces the console to "downgrade" which in ordinary circumstances would not be possible. Custom firmware grants complete control over the console, having access to LV0 (bootloader), LV1 (hypervisor), and LV2 (kernel). This allows users to run homebrew, load game backups, bypass region checks, change fan and CELL/RSX speeds, grant access to root keys, as well as run PS2 ISOs on unsupported backwards compatible models. Some custom firmware implementations reinstate features Sony removed such as "OtherOS". Another popular softmod is PS3HEN. This softmod uses a WebKit exploit to install a signed file through the PS3 Web Browser, then uses another WebKit exploit as well as kernel exploit which grants LV2 kernel access when executed. As opposed to custom firmware, this is a tether softmod meaning PS3HEN has to be activated every time the console is powered on, however it supports all models of PS3 consoles. Users on official firmware 4.84 or later need to install hybrid firmware (another type of unofficial firmware), as Sony only removed the WebKit entry point but hybrid firmware reinstates it. This softmod shares a lot of custom firmware features - users can run homebrew, load backups of games, bypass region checks, and change fan speeds. The unofficial PS2 backwards compatibility is diminished as users can only run PS2 Classics encrypted PKGs instead of ISOs. The hypervisor is still intact and periodically checks if the current code being run is unsigned, there is a small chance if the current code is unsigned, it can lead to the console becoming unresponsive or shutting down, making it less stable than custom firmware. Hybrid firmware is recommended in general when using PS3HEN even if below official firmware 4.84 because it also contains fixes that help stabilise the console in a softmod state compared to official firmware. Softmods for PlayStation 4 The PlayStation 4