Google PRINCIPLES OF MOBILE SITE DESIGN: DELIGHT USERS AND DRIVE CONVERSIONS - Manual (Page 21)

11. USE EXISTING
INFORMATION
TO MAXIMIZE
CONVENIENCE
For your registered users, remember and pre-fill
their preferences. For new users, offer a third-party
checkout service they may already use. Several
retail sites in the study offered third-party payment
services as an option, reducing purchasing friction
for users of those services and allowing the site
to prefill shipping info.
Key Takeaway
Take advantage of information you
already have, and/or use third-party
payment services to make conversion
as easy as possible.
Example from Delta Mobile Site.
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