The most popular and user-friendly tools for this purpose are:
For 99% of retail PS4s: Once you burn an efuse, you can’t un-burn it. ps4 tool downgrade v1.00
A technician must open the PS4 and solder a device (like a Teensy or Raspberry Pi) to the motherboard's NOR Flash memory chip and the Syscon chip. The most popular and user-friendly tools for this
Legitimate homebrew development focuses entirely on running user-created, open-source software, legal emulation, and specialized Linux distributions on owned hardware. Conversely, downloading or distributing copyrighted game backups remains illegal under global copyright laws, such as the Digital Millennium Copyright Act (DMCA). Summary of Core Concepts Status / Reality Non-existent; typically a scam, malware, or adware vector. Software-Only Downgrades typically a scam
Depending on whether you want to downgrade your (the OS) or a digital game (to play v1.00), the methods are completely different. 1. Downgrading Digital Games to v1.00 (No Soldering)
Use a hardware flasher (like a Teensy or Raspberry Pi) to dump your NOR and Syscon flash.
A technician unsolders the Syscon chip and the serial flash memory chip (NOR flash) from the PS4 motherboard. They connect these chips to an external hardware programmer (such as a Teensy or Raspberry Pi) to patch the internal firmware tokens back to the previous state.