Putting the ZIP code first in address forms could auto-fill city, state, and country from a single input, potentially improving e-commerce checkout conversion rates. However, the approach has real-world complications: it feels unfamiliar to users, requires reliable ZIP code lookup APIs (the demo site's API is currently broken), and ZIP codes vary in format and aren't globally unique, making country-first arguably more correct. Stripe Elements is highlighted as an example of a checkout form that prioritizes conversion but doesn't use this approach. The broader takeaway is that form UX should leverage autocomplete attributes, geolocation, and smart backend processing to reduce friction.
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