Title: 15-40 characters.
Body: 140-180 characters.
At Batch, we do advice 15-40 characters limit for your title and 140-180 characters limit for your body description.
If you create a long message more than 200 chars, not all 200 characters will be shown to the user; it will depend on whether the notification is shown as an alert on the lock screen or when the iPhone is actively used.
We recommend you to keep your title and your body message as short as possible. Your title must be “punchy” to attract users. Moreover, we advise you to test your message on different devices and see how your message is displayed before sending them to your users.