Joint bank accounts and any other assets that automatically transfer to the owner that is still living do not need to go through probate as long as the other person listed on the joint bank account is still alive.
The bank account is then automatically owned by the other person who's listed on the joint bank account and is still alive.
Now if both people died and they're listed on the joint bank account and the bank account was not automatically willed to any living persons then the bank account or any other assets will have to go through probate.
But if say you and your spouse has a joint bank account and your spouse dies and you're still living then the bank account doesn't need to go through any probate for you to be able to access it since you're listed as a joint owner on the bank account.