What did dinosaurs eat?

Some dinosaurs were herbivores (eating only plants), others were carnivores (eating animals including other dinosaurs), and some were omnivores who ate both meat and plants (these were mostly scavengers).

Different species of dinosaur ate many different things, depending on their size and adaptation to the environment. Pretty much anything alive (even non-organic matter, such as stones and rocks) was likely to find its way into the stomach of a dinosaur. The size of the largest herbivores and carnivores meant that they had ravenous appetites.

A dinosaur's diet depended on their digestive system, their size, and what kind of food existed at the time. For example, small herbivores would find it impossible to reach the leaves of tall trees, and therefore subsisted on shrubs and low bushes.

Well, different dinosaurs ate different things. Theropods, like T-Rex, Spinosaurus, and Allosaurus ate other dinosaurs or large animals. Here, let me show you some of these Theropod's top prey:

T-Rex-Triceratops, Parasaurolophus, etc.

Spinosaurus-Large Fish or medium-sized dinos

Allosaurus-Juvenile Sauropods, Stegosaurus, other Allosaurus, etc.

And then there were the Sauropods, Stegosaurs, Ceratopsids, Duck-Bills and other that ate plants, and sometimes rocks to help them digest food, like today's birds.

Finally, there were scavengers like Velociraptor, Utah Raptor, Deinoychus, Coelophysis, Dilophosaurus, Oviraptor, Compsognathus and Trodon, who ate eggs, small mammals, medium or small dinos, each other, bugs and more, and they usually hunted in packs.

There were many types of dinosaurs, and they had an equal variety of diets. Some, such as Tyrannosaurus rex and Allosaurus were large meat eaters that ate plant eating dinosaurs. Others, such as Spinosaurus, waded in swamps and ate fish. A few ate insects, such as Compsagnathus. Some, such as Oviraptor and Ornithomimus, ate both plants and animals. Last, but by far the most common, were plant eaters, including Triceratops, Stegosaurus, Ankylosaurus, and Apatosaurus (sometimes called Brontosaurus).
Carnivorous dinosaurs like Tyrannosaurus rex or Albertosaurus ate meat, including other dinosaurs. Herbivore dinosaurs like Brontosaurus or Diplodocus ate vegetation. Omnivore dinosaurs ate both meat and plants.
Dinosours ate leaves from trees or shrubs, (if they were a herbavore), and smaller creatures (if they were a carnivore).
Carnivorous dinosaurs like Tyrannosaurus rex or Albertosaurus ate meat, including other dinosaurs. Herbivore dinosaurs like Brontosaurus or Diplodocus ate vegetation. Omnivore dinosaurs ate both meat and plants.
Dinosours ate leaves from trees or shrubs, (if they were a herbavore), and smaller creatures (if they were a carnivore).