Yes, cabbage is safe for cats to eat in moderation, though it's not a particularly common addition to the feline diet.
Cabbage is rich in essential vitamins and minerals such as vitamin K, vitamin C, folate, potassium and calcium, which are all beneficial to your cat's health. Just keep in mind that feeding your cat too much cabbage can cause digestive issues like gas, bloating or even diarrhoea due to the vegetable's high fibre content.
Make sure the cabbage is cooked, as your cat might have more trouble digesting it in its raw form. Also, make sure it's prepared without any seasonings, oil, or butter, which could cause gastrointestinal illness. Some common complements to cabbage, like garlic and onion, are actually toxic for cats. Plain cabbage is the only option.
If you do feed your cat cabbage, make sure you only do so in moderation, as an occasional snack. Remember, cats are obligate carnivores, which means they need to get most of their nutrients from meat-based foods. Vegetables like cabbage should never displace the meat in your cat's diet.
As always, before introducing a new food item into your pet's diet, consult with your veterinarian first! If your cat eats cabbage (or any food) and is showing signs of illness such as lethargy, diarrhoea, or vomiting, reach out to your veterinarian immediately. If your pet requires veterinary care due to something they ate, cat insurance can help cover the cost of treatment.