I actually think physically writing things down helps you to remember things better.
I don't know if there's any truth to that but
That said, I jot things down in my Notes app so I don't lose a piece of paper.
So for these holiday sales, I had a list of items I wanted to buy. It helps to remind me what I need/want but also keeps me from getting reckless, buying junk.
For groceries, it helps to write it in my phone because I don't make a shopping list all at one time. Today I might put that I need egg whites and frozen blueberries. But then 4 days from now I'll be in the bathroom and realize that I need to stock up on toilet paper or face moisturizer. Plus it helps because I don't buy everything at 1 place. Some things I'll get at the supermarket, others I'll get at Amazon/Sam's Club/Costco, etc....