Old paper logs used by NYPD officers to track their daily activity have now been replaced by an app on cops’ phones, officials revealed Monday.

But the woman who made it happen told The Post it was no easy feat to convince the 175-year-old department to ditch the traditional pen and paper method to join the 21st century.

“When I told people that this is what we were going to do and this is what we should do, people laughed at me. One person said, ‘You go get em, kid,’ ” said Jessica Tisch, who spearheaded the upgrade in her former post as the NYPD’s technology chief.

“I don’t think people thought it was something that would work.”

Cops had been scribbling down the details about the issues they confronted throughout their day in leather binders.

But Tisch — who now heads the city’s Department of Information Technology and Telecommunications — believed the laborious paper method needed to be tossed for something more efficient and began pushing for the technology a few years ago.

“One of my pet peeves is seeing all these inefficient processes in the police department, meaning processes that could be better with the use of technology,” Tisch said. “For me one of the most glaring was the activity log.”

“Imagine how many activity logs officers use every year,” she said of the NYPD’s roughly 36,000 members. “So the activity log for me for a very long time was one of the most appealing candidates for modernization. For me it was like the holy grail.”

Tisch says she initially received pushback from those around her at NYPD headquarters in 1 Police Plaza when she proposed the digital log.

But the brass warmed to the idea when they realized it would make it easier to comply with the state’s new discovery law, which requires district attorneys to share detailed information about crimes with defense attorneys within 15 days.

It also gives bosses a way to see exactly what cops are doing, and links up with a separate 911 app on officers’ phones.

The department started to roll out the e-log city-wide in early January after test runs in a few precincts, and it is now on every cop’s department-issued phone.

“As of today, everyone is supposed to use the digital activity log,” Tisch said. “The paper books will no longer be authorized.”