Obviously, only cats with outdoor access will be able to eat grass of their own volition, but all cats might enjoy cat grass, which we'll cover later in the article.
Grass is a digestive aid.
It may seem like a weird thing to do, but eating grass isn't necessarily bad for your cat. In fact, it might even be beneficial. One reason cats eat grass is because it acts as a digestive aid. In the wild, cats often eat grass after consuming their prey. Grass stimulates a cat's urge to vomit, which rids their system of the indigestible parts of the prey. Our pet cats don't need to purge animal bones from their systems, but they do need to rid themselves of things like hairballs and other detritus that may be clogging up the works.
When is grass not safe?
The one thing to watch out for is that not all outdoor grass is safe for cats. Outdoor grass can be riddled with pesticides, which are toxic to your cat. So if you take your cat outside on a harness, watch them carefully, and don't let them consume other people's lawns if you can help it.
Grass has vitamins and minerals.
Another reason cats eat grass is for vitamins and minerals. Cat grass contains small amounts of vitamin A, vitamin D, and niacin, all of which are beneficial to a cat's body. (The same is not necessarily true of "outdoor" grass, of course, but cats don't know that.) If you have an indoor cat, cat grass is a great way to get them some extra vitamins and minerals, as well as keep them entertained — many cats love batting it around in addition to eating it.
If your cat likes to eat outdoor grass, the best thing to do is to offer cat grass as an indoor alternative. Cat grass provides a tasty, vitamin-rich alternative to the less-safe option of outdoor grass.
And as always, check your shoes for cat puke before you put them on.