Imagine: You’re skimming your Twitter feed and notice a stream of sad tweets from a college friend. Without a moment’s thought, you send a funny GIF across the digital divide, content that you’ve cheered up your friend and made a positive mark on their day.

But, wait: You can’t quite remember where they’re living these days, or what they do for work. Did you miss their birthday? Chances are, you pop over to Facebook and check, reassure yourself that you’re caught up on their milestones, then go about your day. Are you still friends, even though you haven’t seen each other in years, or spoken in a non-digital medium?

Are all those tools for staying connected actually making you a worse friend?

New Yorker Gary Johnson, 38, isn’t on Facebook and doesn’t get those daily nudges to “help [insert name here] celebrate.”

“My friend told me that our other friend recently got engaged, and so I called him and he really appreciated it,” Johnson told The Post. For Johnson, joining countless others in boycotting social media brings peace of mind when it comes to keeping up with the lives of “friends.”

“It doesn’t matter to me whether people know about my personal milestones or not,” Johnson continued. “My real friends typically call me on those occasions, and that’s all that matters to me. Not Facebook congrats and birthday wishes.”

And contrary to popular belief, even millennials can find the expectation of remembering online acquaintances’ events exhausting.

“I feel really lazy that I can’t remember any events or phone numbers” without online reminders, 27-year-old Nathalie Devin, who lives in London, said at first. But on second thought, she explained that she “doesn’t really feel bad about it because it’s the norm these days.”

Could it be possible that given enough time, those who choose to forgo an online presence are fast forgotten? For Devin, it’s their loss.

“I can’t even think of all the friends I used to have who aren’t online,” she reminisced. “I don’t remember any of their names at this point.”

Human interaction online tends to reflect real-life, centuries-old customs, according to Karen North, professor of digital social media and director of the Annenberg Program on Online Communities at USC Annenberg School.

“Humans, by nature, have always been social animals,” North explained. “The only difference is that these days, the socializing is being done more online than face to face.”

In this day and age, people are not very likely to care what your source of information is, North noted.

“There’s more of an expectation that people know about major life events because they’ve been announced on large public forums.”

According to North, it used to be that you either heard about something from a friend or didn’t. “It was sort of on the announcer to reach all the groups when something good or bad happens in their life.”

People who’ve opted out of social media often miss these important — and admittedly, sometimes mundane — announcements. “They have to recognize that they are missing out,” North said. This is because these days, the issue is that the people online don’t usually feel obligated to reach out and announce things in any other way after posting about it.

For some, the result of not being an internet voyeur has daunting consequences.

“That’s the one thing I do wish I had social media as a tool for,” said 28-year-old James Wetter, who lives in Melbourne, Australia. “I feel bad that I don’t contact friends or family more often.”

For Wetter, “On the one hand, I don’t want to be on social media for privacy reasons,” he explained. “But I miss out on certain conveniences when it comes to keeping up with people, and I feel guilty about that.”

But perhaps people offline don’t have as much to worry about as they think. Online shortcut tools are well and good, but according to North, some studies have shown there is actually a reduction in communication and contact.

“The problem is that people will ‘reach out’ by clicking on a friend’s page and reading through their posts, and that way they feel engaged even though the engagement was one-sided,” North noted. “So the relationship doesn’t actually get furthered, it’s just peering into each other’s lives.”

And then there’s the question: Is being a supportive online friend even enough?

“Even when they see something good happening to someone and you ‘RT’ or ‘Like’ something, it’s not always seen as enough,” North explained.

So, for things like birthdays, people write “Happy birthday” on Facebook, but don’t necessarily get a lot of credit for jumping on the bandwagon.

“This is because there is social capital involved,” North said. “Social interactions are now valued on two different levels: One is the public, easy response on social media, and the other is the much more valued one: private contact.”

In other words, human nature indicates that calling a friend to congratulate them on the baby news will always gain you more points than just double-tapping their pregnancy reveal on Instagram.

And because of the social capital involved, most people’s efforts — whether a quick G-chat message or a bouquet of flowers — are deeply felt.

As North puts it, when you wish a friend a happy birthday on their wall instead of in person or on the phone, that friend typically makes a mental note of your online interaction vs. a personalized one-to-one wish.

“Humans are known to keep tabs on friends and family’s interactions,” North explained. “And so, when you put in the bare minimal effort, it really does show.” So perhaps you’re not necessarily labeled a “bad friend” for opting for a quick social media thumbs up to a friend’s life event, but in the long run, the friendship tends to be affected by your lack of “real” effort.

“The social rules are more complicated these days because we don’t have the real-life social cue to tell us if someone is appreciative of our connections or not,” North said.

Brian Solis, who is interested in “digital anthropology,” said the possibility of being a so-called “bad friend” for opting to go mainly digital is something people are still adapting to.

“We are getting lazier, and so putting something on a wall is checked off as a personal interaction for most people,” he said. “But we’re learning the hard way, through experience — so there really is no answer to the ‘bad friend’ notion. It’s all user-defined.”

As for those who keep off social media, Brendesha Tynes — an expert on social media and adolescent development online and an associate professor of educational psychology at the USC Rossier School of Education — told The Post: “People who aren’t on social find other ways to communicate.”

They may not be wishing everyone they’ve ever met, like their college roommate’s cousin they met at a party that one time, a happy birthday on Facebook, but they’ll catch the important milestones if they put in the effort.

“The relationships can be just as rich as if the person were on social media.”

Non-social media denizen Johnson, for example, prefers to take a loose approach and trust things to work out.

“I like to leave things up to fate,” Johnson said. “If I’m meant to cross paths with someone and wish them ‘happy anniversary,’ it will happen without social media.”

And when it comes to getting a free pass on keeping up with friends’ lives, Johnson put it simply: “Everyone’s lost these days — people forgive me because I’m not on social media.”