How can i get a unique user id for two apps

REST API
#1

I have two apps, and the id of one kakao user in two apps is different. How can I make the id to unique or connect these id by using a api.
for example :
one api is /v1/user/me, I user my kakao account to ask this api by two app, and the return id is different.
return:
{“id”:558533059,“properties”:{“profile_image”:null,“nickname”:“tracy1993”,“thumbnail_image”:null}}
{“id”:558531491,“properties”:{“profile_image”:null,“nickname”:“tracy1993”,“thumbnail_image”:null}}

#2

@anon55674244
Sorry, we don’t provide a unique id for user’s account. the ‘id’ property is user id of a specific app.

#4

hi I have another question? Do you have a rest api to get user’s friend list ?