What's on the SIM card?

I will soon switch from an Apple iPhone to a Huawei. My question is whether contacts are stored on the SIM card or whether I better write them out.

That is different, with Android it can be selected. Just check when the new cell phone is there and if not then write it out to avoid unnecessary work.

Best wishes

P. S. Huawei was a good decision

Contacts are stored on the cloud or locally on the device, depending on what you have selected.

But not on the SIM card. There's usually Only your mobile number and the telephone provider on it

In the contacts you can set that the contacts should be saved on the SIM card

It is entirely up to you whether you have previously set whether the contacts will be saved on your SIM. By default, they are saved on the device.

With a smartphone, you can see how much you have saved on SIM in the file manager.

That is not right. In the past, when the phones were not smart, the phone directory was saved on the SIM card. Later the phones had their own phone books, which were more convenient, then the smartphones came. However, the function of saving contacts on the SIM still exists. And not only a few users unintentionally end up with entries that are "inexplicably" gone after changing the SIM.

Okay, I didn't know that exactly.

Your contacts (only name and phone number) are only saved on the SIM card for key cell phones, not for smartphone. In the device menu, however, you can transfer / copy SIM card entries to your smartphone.