The guides explain how circuit training is put together. These do it. Both run in the browser, neither wants an account, and nothing you enter leaves your device.
BUILDER
Give it your minutes, your level and what's in the room. It fills all six movement patterns, orders the stations so no two in a row work the same thing, and solves the rounds backwards from your time.
TIMER
Runs 30/15, Tabata 20/10, 45/15 or anything you set. Hand it a circuit from the builder and it names the station you're on and the one coming next, so nothing has to be memorised.
They are meant to be used in that order: build once, then run the same session for three or four weeks. The builder has no reshuffle button on purpose, and the guide behind it explains why a circuit you rebuild every session can't tell you whether you're improving.