Paramount+

• If you subscribed to Paramount+ in the Paramount+ app on an Apple device, then it would be available in the Paramount+ app on any of your Apple devices with the same Apple ID account.
• If you subscribed to Paramount+ as a Channel in the Apple TV app, then it would be available in the Apple TV app on any of your devices, when signed in with the same Apple ID account.
• If your subscribed to Paramount+ with Paramount+ directly, then you would sign in to the Paramount+ app with your Paramount+ account. It would then be available on any device (and any platform) with the Paramount+ app.

These types of subscriptions have different terms and conditions, different perks and limitations, and are mostly* not exchangeable as such. See below for the exception in your favor.

*Subscribers to Apple TV app Channel Paramount+ can “verify” their subscription with Paramount, and then also access Paramount+ outside the Apple TV app, through the newly created Paramount+ account. This is a one-way crossover for just this channel.

How do I stream on paramountplus.com or the Paramount+ app with a channel subscription? - Paramount+ Help

Verify your Apple TV Paramount Plus channel subscription - Paramount+

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Subscribe to Apple TV channels in the Apple TV app - Apple Support

Apple TV Channels FAQ: Services, pricing, availability, and everything else you need to know - Macworld (US)

Paramount+ app - App Store preview - Apple