Cryptocurrencies can be kept online or offline. If the cryptos are kept on the exchange platforms or other online platforms, it can be lost due to hacks.
So it is important to choose the best wallets that are safe and secure. Please help me in choosing the safest cryptocurrency wallets
For altcoins, hardware wallets are the best because you can store multiple cryptos in a same device and can keep the wallet offline unless you are going to make a transaction.Ledger and Trezor are the best ever hardware wallets which itself have different models so pick the best one depends on which cryptos are going to be stored in it.