Dogs can eat some cat food.
Although cat food contains mercury content that in large enough doses could be deadly for dogs.
But it's okay if your dog happened to eat some cat food but I would not recommend feeding your dog cat food constantly.
But in moderation dogs can eat some cat food.
Just like cats can eat dog food the dog can eat cat food.
Although cats can safely eat more dog food because it does not contain mercury and mercury content is okay for cats but not for dogs.
Dog food though is best for dogs and cat food is best for cats.