Is cat littler safe to use for rabbits?

I just adopted a 2 year old lion head, he is litter box trained and the family I got him from provided me with food and hey to start, but no litter. He wasn't pooping in his box and I figured it was because his litter was very dirty but I hadn't bought any yet (it was the day after I got him) so I used some cat litter we had at the house for the time being but it seems like he likes it more. He's been digging around in it and i've noticed that it smells much better then whatever was in his box before. I have read some things online saying certain brands are okay and some are not and it's a lot of info to take in so, help!! I want my bunny to be safe, can anyone suggest something safe that I can pick up at a local grocery store, petstore, or walmart?