Modern bidet seats and bidet attachments are designed to fit most standard “two-piece” toilets, which includes a bowl, a tank, and a flexible steel hose connection between the water supply and tank. You’ll know you have this toilet if all of the water supply connections are visible.
If you have a skirted toilet or a commercial “flushometer” toilet, you may need a special adaptor from your bidet company.
French curve toilets are generally no-gos with a bidet attachment because the curved shape of the bowl makes it difficult for a bidet to sit flat.