Every Battle Cats save has an internal RNG seed that decides every gacha roll. Enter 7-10 cats you already rolled, in order, on one banner, and this tool finds which seed produced them — then you can preview exactly what any banner will roll next, before you spend cat food or rare tickets.
The seed only changes when you roll rare gacha, and it is shared across every banner on your save. Once found, your seed lets you preview upcoming rolls on any current banner without guessing. This uses the same reverse-engineered RNG math as the community battle-cats-rolls project, ported to run entirely in your browser and on this site's own server — nothing about your save is ever transmitted, only the cat names you already remember rolling.
No. You type in the cats you remember rolling; nothing is read from or written to your device or game save.
Each additional roll narrows down which of billions of possible seeds matches what actually happened, until only one (or very rarely two) remain.
No. One seed drives every rare-gacha roll across your whole save, so a seed found on one banner still predicts rolls on any other.