A small change in ticketing policy at the TD Garden, instituted quietly over the winter, sheds an interesting light on shifts toward wider-scale digital ticketing initiatives at the home of the Celtics and the Bruins.

Garden ticket holders are no longer allowed to enter games using a copy of their tickets on their phone. In other words, if you have a PDF form of your ticket, you must now print it out in order to enter the event. Until January, guests had been able to gain entry by showing the PDF on their phone, as ushers would scan its barcode.

Instead, guests who buy directly from the Garden’s ticketing partner TicketMaster, can now access their tickets on the TicketMaster website or app, or they can ask TicketMaster to send the digital ticket right to their phones, where it can be stored on their iPhone’s Passbook or its equivalent on other operating systems. These new tickets carry individualized QR codes.

Garden spokesperson Tricia McCorkle says that the shift is meant, in part, as a security measure. While scalpers or other secondary ticket market sellers could conceivably scam customers by forwarding the PDF version of the ticket to multiple recipients, the new digital tickets are exclusive to one ticket and one device at a time.

The Garden still accepts printed PDFs, so scalpers could accomplish the same means by printing out several copies of the ticket and distributing them. But the Garden eliminates scammers’ digital avenue with the policy change.

The change has had a larger effect on the broader Boston ticket economy as well.

The new mobile ticketing service applies only to tickets bought directly through TicketMaster. That means that guests who buy tickets from resellers like StubHub and Ace Ticket—both of whom send PDFs of tickets to guests via email—can no longer gain access to Garden events through their mobile phones.

StubHub spokesperson Glenn Lehrman says the Garden is the first venue to have enacted the policy, as far as the company is aware. Lehrman says the policy makes sense for the security reasons McCorkle described, and expects other venues to eventually follow suit.

It has, however, caused some issues for ticket holders who are turned away when presenting the PDF on their phones who are told that they need to print out their tickets.

The unfortunate customers have the option of using the StubHub office—about a five-minute walk from the Garden— to print their tickets or they can try to talk an area hotel into doing so. That’s little consolation to customers who might plan to arrive just in time for tip-off and wind up missing half of the first quarter because they were busy looking for a printer.

(The Garden will not print tickets for those customers for the same reason they do not accept PDFs on a mobile device: the inability to guarantee their authenticity.)

As a result, Lehrman says, StubHub now sends email alerts to purchasers of Garden tickets the day of the event, reminding them to print out their tickets. The situation also puts the onus on the company to make their tickets compatible with the Garden system—which would likely require creating a marketplace for TicketMaster’s digital tickets. StubHub already offers a similar system to TicketMaster’s for its partner venues and organizations, a group that includes the Red Sox.

Ace Ticket CEO Jim Holzman was not aware of the policy shift before BetaBoston contacted him, but said his company is working on developing more mobile options for customers. Because Ace owns its tickets, it might have an easier time finding a solution than StubHub, which serves as a marketplace for individual resellers.

The change is indicative of a wider shift at the Garden toward broader digital ticketing, the venue’s vice president of technology and e-business, Lorraine Spadaro said.

Spearheading those initiatives are the Celtics, who are considered at the forefront of ticketing technology in the NBA. For example, the Celtics introduced the Parquet Pass—a reusable card holding every ticket—to season ticket holders this year.

Paul Cacciatore, the Celtics’ senior director of business operations, says the card has already been adopted by 70 percent of season ticket holders. Future plans call for using the pass to also carry stored value for things like concessions and souvenirs.

Spadaro says the Bruins are planning to follow suit with similar initiatives. Meanwhile, the Garden has hosted a number of concerts that have opted for digital-only ticketing in recent years.