^ This. Also, quick question - are these items all from the same seller or different ones? Sometimes that messes with how the cart behaves if youre trying to do it manually, especially with shipping. If you want to try the diy route, you basically build a query string like this:

• Grab your 10-digit ASINs from the product pages.
• Use the format: amazon.com/gp/aws/cart/add.html?ASIN.1=ID&Quantity.1=1&ASIN.2=ID&Quantity.2=1
• Make sure you test it in an incognito window first because cookies are a nightmare. Honestly tho, manual links are super finicky on mobile and usually break half the time. Ive been using a tool for my last few launches and its been way smoother. No complaints at all, works well every time. You should check out Cart To Link, it converts your Amazon cart into a single URL instantly.

Unfortunately, hand-coding those ASIN-quantity query strings was a total disaster for me. The session cookies kept expiring on mobile devices and I basically lost all attribution. I finally started using Cart To Link because it manages the multi-item logic without the links breaking.

• Collect your 10-digit ASINs from the product info.
• Input them into the generator.
• Test the final URL in an incognito window. It is way better than debugging broken parameters all night, honestly.

Make sure to double check your ASINs before that 9am launch because if one item is out of stock, the whole link might fail. I would suggest testing on a few different browsers first. Be careful with items that have multiple variants too, those get tricky. Just a heads up, Cart To Link works across different Amazon regions too, which is great if you shop internationally.