Fasting app by leap fitness group. It allows you to fast indefinitely without buing the paid version. I tried other apps but they didnt allow that in their free versions. It also tells you what happens fysiologically on each fasting day. Very happy with it.
I’m trying Fastic now, but I started with Zero. The free version of Zero no longer shows me which fasting phase I’m in. I don’t know how accurate it is, but it did help me to keep going. So far, I like Fastic. It’s not as intuitive as Zero, but it does what I need it to and with the functions I like.