Deep link vs deferred deep link: do we actually need both?

Both, if any of your links reach people who do not have the app yet. Universal Links and App Links only route users who already have it installed. For everyone else, neither store passes your link parameters into the new install, so the first open starts with no memory of the click. A deferred deep link stores the destination and campaign before the store redirect and hands them to the app on first open. Split it by channel: paid acquisition links mostly reach non-installers, so they need deferred, while email, push and CRM links mostly reach existing users, so a direct deep link with a web fallback covers them. The same stored click also credits the install to the campaign instead of organic. To test it, delete the app, tap the link, install from the store, and confirm both the screen and the campaign. How it works: https://linkrunner.io/deferred-deep-links