Turn off mobile phone before inserting / removing SIM card ?

Is it safe to change the SIM card without switching off the smartphone ? Should I turn off my mobile phone before inserting or removing SIM card ?

When you are changing the SIM card, it is possible to do it without turning off the phone and usually everything works allright. But for a safety reason, it is recommended to power off the phone before inserting or removing the SIM card.

Powering off the phone before inserting or removing the SIM card, is recommended by some mobile phone manufacturers and also by some mobile operators.