A 37-year-old Boston mother was commuting to work this month when a power outage hobbled the Orange Line. The disruption forced her onto three different trains and a shuttle bus, and then, when she and the other passengers finally arrived at Back Bay Station, they had to pay again to get back on the subway.

So like any millennial with a gripe and a smartphone, she took the issue to Twitter, tagging the MBTA in her post.

“Good morning, Mayor Wu,’’ the regional transit agency quickly responded. “Orange Line Officials were responding to Back Bay and Jackson Square to look into this when you reached out. We apologize for any inconvenience.’’

“Thank you!’’ she chirped.

Meet Boston’s first millennial mayor, now active on your favorite social media platform. Just over two months into the job, Michelle Wu is already changing the way her office operates, especially online. She interviews public health experts, meteorologists, and city employees on frequent Instagram live videos. In addition to @MayorWu, the official handle run by her staff, she continues to run her own personal Twitter handle, @wutrain, where she promotes city policies, engages with residents, and occasionally shares photos of her brunch.

That high-octane online presence is a testament to how much city government, and its image, has changed since the pre-Internet era, when news from the mayor arrived once a day with the morning paper. Social media provides a crucial opportunity for Wu to stay in direct touch with constituents, bypassing traditional media gatekeepers and whatever additions and subtractions they might make to her message.

For a world still getting to know Boston’s young new mayor, it offers a glimpse into her personality as well.

“She is changing that sort of . . . traditional, male, stuffy, formal, mayoral office tone,’’ said James Hills, who hosts the Facebook livestream “Java with Jimmy’’ and worked in City Hall under former mayor Thomas M. Menino. “People will perceive the office of the mayor differently.’’

Wu’s online presence is hardly the chaotic governance-by-tweet of Donald Trump, who fired off a nonstop stream of braggadocio, vitriol, and misinformation, the last of which earned him a permanent ban from Twitter. Her style on social media, much like her manner in person, is polite but direct. As with the MBTA interaction, she is not shy about drawing attention to problems, even if her colleagues in government might prefer she keep those discussions offline. Nor does she respond only to positive posts or to accounts with a great reach. She answers routine questions and defends her policy decisions, while also making time to crowdsource recommendations for office decor.

The @wutrain account at once presents a staid public servant, a modern-day influencer, and a one-woman rapid-response team.

When a journalist tweeted that the city was demolishing tents at a homeless encampment without checking whether anyone was inside them, Wu sought to set the record straight. After Governor Charlie Baker said at a news conference that Boston had declined help for its understaffed bus routes, she pushed back on the governor — gently but firmly — in under 280 characters. Baker had offered drivers licensed for small vans, not school buses, she pointed out.

“Works for some districts but not Boston,’’ she asserted.

She shares photos ranging from formal State House ceremonies to snow day shots of her sons. She responds to fans and trolls alike.

When a critic asked “Masks not necessary?’’ about an old photo of Wu with her face uncovered, she responded curtly: “4 years ago, no.’’

Wu uses social media in the rare moments of respite between mayoral responsibilities. Sometimes, that’s during her morning commute.

Often, it’s in the evenings, after her two young sons have gone to bed.

And there’s no particular formula to who gets a reply from Boston’s mayor.

Social media is not just “a place where I put things I want people to read,’’ Wu said in an interview earlier this month. “I try to respond where I can . . . . I just look at who’s tagged me, and what issues people are talking about, and if I can provide something helpful or try to answer a question.’’

As often as Wu provides answers, she seeks them. Think of it as the digital version of her Orange Line commute: Come one, come all, and tweet your mayor what you’re thinking.

The responses often get her attention.

“You can ask my team — every meeting, I’m like, ‘Oh, someone DM’ed me this, or I saw on Twitter that this or this,’’’ Wu said.

It’s new territory for City Hall, where not so long ago, Wu’s mentor Menino resisted the use of voicemail. The overflowing paper files of former mayors have given way to Google Docs and Google Sheets, which Wu sometimes edits on her iPhone on the subway. Her office tries to limit its paper usage, aides said, and staff communications often take place on iMessage or Signal.

Wu is hardly the first Boston mayor to engage online. Former mayor Martin J. Walsh had a Twitter following of 325,000 and held question-and-answer sessions on Reddit and Twitter, once even commenting on Zayn Malik’s departure from the band One Direction (“We must soldier on,’’ Walsh lamented).

Still, “it’s different with Mayor Wu,’’ said Dave Sweeney, who served as chief of staff to Walsh.

“You could see her using these tools if she weren’t mayor,’’ Sweeney said. When Walsh used social media, he added, “I’m not sure that the audience really perceived it as natural as what they’re going to perceive from Michelle Wu.’’

Some of that is purely generational. Like many her age, Wu has witnessed immense technological disruption. She remembers the days before cellphones, but uses Instagram fluidly. She was a Harvard undergraduate when one of her classmates invented Facebook — and she was in the public eye as the platform got replaced by newer, cooler alternatives.

Those advances in technology have helped facilitate an ongoing trend of “personalization in politics,’’ said Daniel Kreiss, a political communication expert at the University of North Carolina Chapel Hill.

“What social media does is give politicians access to audiences in a much more immediate way and a much greater way, in terms of scale,’’ Kreiss said. Wu’s Orange Line tweet — much like her Orange Line commute — is a way for her to say, “ ‘I’m one of you and I’m attentive to your problems,’ ’’ he added.

It’s a savvy political strategy for a mayor whose victory was powered by a strong online presence and an army of young supporters.

“We want to make sure that we’re communicating policy in the places where young people are already talking to their friends, getting their information, getting their news, spending their leisure time,’’ said Paulina Mangubat, digital director for the mayor’s office. “A lot of that happens online.’’

Still, experts warn that there are risks to that direct, unfiltered contact. It can empower politicians — think of Trump — to promote misinformation, leaving journalists and experts little opportunity to correct it, said Jennifer Grygiel, a Syracuse University professor who studies social media.

“With so many politicians using [social media] to grow and cultivate really large audiences, they essentially have their own broadcast channels,’’ Grygiel said. “That’s risky business.’’

And there is a dark side to being a mayor who is extremely online: Sometimes hateful responses to Wu’s policies get piped directly into her cellphone.

“ALREADY the WORST MAYOR BOSTON EVER HAD!’’ one person opined in the comments of a recent Instagram live. “No one wants you here,’’ another user informed her. (A few lines lower, a different voice chimed in: “Thank you Mayor Wu! You’re doing a great job!’’)

But often, Wu makes light of those critics, replying to them all the same.

“You win,’’ one Twitter user spat at Wu earlier this month, posting a vaccine card with one recent dose recorded, a week after her vaccine mandate for indoor establishments went into effect.

“YOU win, my guy,’’ she replied, emojis and all.

Emma Platoff can be reached at emma.platoff@globe.com. Follow her on Twitter @emmaplatoff.