This procedure is for educational purposes only. It will void your warranty, may brick your console, and requires advanced soldering skills.

I stumbled across the "PS4 Tool Downgrade v1.00" while trying to revive a console accidentally updated to 12.00 from a jailbreakable 9.00. In theory, this tool promises to force a firmware downgrade to 1.00 — yes, the original launch-day firmware.

: Specialized utilities like PS4 Wee Tools are used for chip patching. PS4 Firmware Downgrade: Reverting from 11.02 to 11.00

: It is significantly easier and safer to buy a used PS4 that is already running an older, exploitable firmware (such as 9.00 or 11.00) than to attempt a downgrade.

The most common "v1.00" tool refers to proxy-based applications like PSX Download Helper

Let’s analyze what comes up when you search for that exact phrase.

If the console is still on 1.00, dump the NOR immediately as a backup.

If you're an experienced modder with backup consoles, spare time, and soldering gear, this tool is interesting for research. For 99% of users looking to simply "downgrade from high firmware to jailbreakable" — stay away . You will likely brick your PS4. Wait for a safer, software-only method (if ever).