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A reader app refers to an utility that provides content or a subscription to paying users.
Netflix and Spotify are examples of reader apps.
That way, whenever someone signed up for a subscription, Apple could collect a commission from the developer.

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According toThe Verge, that commission went as high as 30%.
Instead, those users had to sign up for the subscription outside the app.
Spotify CEODaniel Ek tweetedthat while this is a good move, the problem still persists.
Ek says developers want fairer rules that apply to everyone equally.
Its unknown whether Apple will extend its new reader app rule to gaming apps or other subscription service.