Can I use a PayPal signup URL to onboard merchants to my marketplace?
Yes, you can do this via PayPal's URL onboarding method, if your marketplace solution follows the Connected path model. The URL onboarding option uses a URL with static parameters to direct your merchants to PayPal, where they'll have to complete all signup fields. You might need to whitelist the URL you pass to return the merchant to your site.
URL onboarding doesn't allow you to prefill any information that you may have already collected from your merchants, but enables quicket merchant setup than other methods. Once a merchant's account is created, we send them a welcome email. The merchant then clicks a link in the email and confirms their email address.
Connected Onboarding Integration Guide