Most of the Greek and Italian, and some Spanish ferry companies, provide e-tickets. You can easily recognize if the ferry company supports e-tickets during the booking process (there is a square pixel icon of a QR code next to the departure time) or check our Ferry Operators' page.
Printing e-tickets is optional, which means that it is not required by most ferry companies except for Fast Ferries in Greece. Therefore, if you are traveling with Fast Ferries, you have to print out your e-ticket. If you are not traveling with the aforementioned ferry company, you can just store and present your e-ticket on your mobile device or tablet when boarding.
To check-in online and get your boarding pass, you can click on the links provided in your booking confirmation email. You can either download your boarding pass on your mobile device or print it out and bring it with you. The most important piece of advice is to make sure your device is fully charged; we all know that having your phone run out of battery is not very pleasant - especially while traveling.