Can I use PaperKarma without a mobile phone /app?

Unfortunately, no.

PaperKarma requires an Android or iOS device to access the service, which entails taking a picture from within the app (or selecting from your image gallery) and submitting the photo for image recognition of the mailer.

These photos also serve as proof you actually received the junk mail at your address, which is required by certain mailers in order to remove you from their database or add you to a suppression list.

Please note, PaperKarma is optimized for smartphones but is also functional across a wide array of tablet devices.