Shopify add multiple products to cart with different properties

Shopify Discussion
5

You just need to name the inputs this way:

<form action="/cart/add" method="post">
<input name="items[0]id" value="29627430142024" type="hidden">
<input id="Customizer1[]" name="items[0]properties[Customizer#1]" value="RTD- 
Design1" type="hidden">
<input id="YourDesign1[]" name="items[0]properties[YourDesign1]" value="1355818798" 
type="hidden">
<input name="items[1]id" value="29644970950728" type="hidden">
<input id="Customizer2[]" name="items[1]properties[Customizer#2]" value="RTD- 
Design2" type="hidden">
<input id="YourDesign2[]" name="items[1]properties[YourDesign2]" value="1355818798" 
type="hidden">
<input name="return_to" value="/cart" type="hidden">
<input value="Many Products" type="submit">
</form>