Mark required and optional fields explicitly
Tell shoppers which inputs are required before validation and keep that instruction available to every input method.
Tell shoppers which fields are required and which are optional before they submit. Do not make validation reveal the rule one error at a time.
Baymard's checkout research supports explicitly marking both required and optional fields.[1] W3C's form guidance supports giving instructions before they are needed and associating inline instructions with the relevant controls.[2]
The rest of this lesson is available once the Atlas is unlocked.