Karlovac tends to be quite safe for solo female travelers. Crime rates are generally low, and people are generally friendly and supportive towards tourists. However, like any city, it's important to always stay vigilant, especially at night or when in less crowded areas. It's also beneficial to understand local customs and behave respectfully. Be sure to always keep your belongings secure and let someone know your plans when possible. The city is not devoid of petty crimes like pickpocketing, but with basic precautions, the visit should be enjoyable and safe.