That’s why you should:
- Never share them with anyone.
Private things don't need and should not be shared publicly with anyone.
- Store them offline (write them on paper or make use of a hardware backup).
Offline, airgap are good ways to store your wallets that have big funds and your wallet backups.
-Avoid saving them in your phone or computer where they could be hacked.
If your device is online, you should not do it.
If your device is used offline, airgap, you can do it but a vital rule is always have different wallet backups. Avoiding a practice of having only a single wallet backkup as you can lose it anytime by accidents.
How to back up a seed phrase?Of course you are right whenever a PC regularly goes online it's not advisable to store our seedphrase there because there is every likelihood to get hacked depending on where those our seedphrase are being stored, especially when it's stored on Microsoft walls. That is, we should stop storing them over such device. Another good way to store our seeds is engraving them on a metal steel plate, this could prevent fire damage or flooding, but in paper you could easily lose them immediately it's wet.