Turkey is generally considered to be a safe holiday destination. Violence and crime occur to a limited extent. If you are staying at a holiday resort or only visiting the touristic areas of the city, probably you will not be confronted with violence. However, you must take into account crimes like theft and pickpockets occur just as much as in any other big city in the world. Especially in the tourist areas, foreigners are easy victims. Therefore, do not wear expensive jewelry and never show that you carry a lot of cash with you. Also keep expensive items such as watches and cameras out of sight. Pickpockets almost never operate alone, and confrontation might end up into physical violence. If you are in areas where you do not see any other tourists, take a taxi to return to the touristic areas.
Because petty crime can have major (financial) consequences, for example when your expensive camera is stolen, it is advisable to take out travel insurance. Travel insurance is also important in case of loss or damage to valuable items, medical costs, accidents and when you are sick or injured.