Packed bars with carousing revelers spilling onto clogged streets. Takeaway booze swigged by drunken tourists and students. Earsplitting volumes in once quiet residential neighborhoods long after midnight.

When Milan’s authorities embarked years ago on plans to promote the city as a buzzy destination by building on its reputation as Italy’s hip fashion and design capital, the resulting noise and rowdy overcrowding were perhaps not quite what they had in mind.

Now, after years of complaints and a series of lawsuits, the city has passed an ordinance to strictly limit the sale of takeaway food and beverages after midnight — and not much later on weekends — in “movida” areas, a Spanish term that Italians have adopted to describe outdoor nightlife. It will go into effect next week and be in force until Nov. 11.

Outdoor seating for restaurants and bars will also end at 12:30 a.m. on weekdays, and an hour later on weekends, so that people who want to party longer will have to do so indoors.

The businesses that have profited from Milan’s success in promoting itself as a happening city are grumbling.

One trade association complained that the ordinance was so strict that Italians would no longer be able to take a late-night stroll with a gelato in hand.

Marco Granelli, the Milan council member who is responsible for public security, said those fears were overblown. Eating gelato on the fly would not be a problem, he said.

The ordinance, he said, was aimed at dealing with “behavior that impacts on residential neighborhoods” and with takeaway alcoholic drinks, which are seen as the main reason late-night revelers linger on certain streets and squares. “It’s clear that ice cream, pizza or brioches don’t create overcrowding,” he said.

Marco Barbieri, secretary general for the Milan branch of the Italian retailers’ association Confcommercio, said his group would fight the ordinance, which he estimated would affect about 30 percent of the city’s 10,000 restaurants and bars. The new rules, he said, would penalize retailers for the bad behavior of their customers.

But residents have been complaining about Milan nightlife for a while.

“It’s a nightmare,” said Gabriella Valassina of the Navigli Committee, one of several citizen’s groups formed to address the increasing numbers of people — and decibel levels — in Milan’s historic neighborhoods.

She outlined a list of complaints: noise pollution (peaks of 87 decibels, well over the allowed 55, according to municipal limits); streets so packed with revelers that it is hard to walk or even reach one’s front door; an exodus of fed-up locals that is changing the character of picturesque neighborhoods.

With the new rules, the city has allocated 170,000 euros, a little over $180,000, to help bar owners hire private security services to stop revelers from loitering on the streets outside their establishments. And it is working with police unions to modify contracts to allow more officers to work night shifts to enforce the new rules.

The city may have been motivated to act more forcefully after decisions by local and national courts in Italy have sided with residents who sued city administrations for not reining in nighttime chaos.

Elena Montafia, a spokeswoman for the Milano Degrado, a neighborhood association, is one of 34 residents of the Porta Venezia neighborhood suing the municipal government and asking for damages on the grounds that inaction to their complaints had put their health at risk.

“Living in Milan has become really difficult,” she said, adding that it was only after a decade of pleading with unresponsive local administrators that she and the other residents had decided to go down the legal route.

Still, she and others doubted that the new ordinance would change much, and that enforcement would be a problem.

“When you have so many people around, there isn’t a law that is going to make them go home; it’s impossible,” especially because the crowds normally far outnumber police officers, said Fabrizio Ferretti, the manager of Funky, a bar in Navigli, one of the affected neighborhoods. He acknowledged he was persona non grata with the owners of the apartments above his bar.

The predicament that Milan finds itself in today comes after years of efforts by leaders to broaden the city’s image from Italy’s financial and industrial capital to a more service-oriented, tourist-friendly one.

A succession of municipal governments has also encouraged the development of the city’s less central neighborhoods, said Alessandro Balducci, who teaches planning and urban policies at the Politecnico di Milano.

One of the inspirations was the Fuorisalone, the sprawling network of events related to Milan Design Week, the design world’s largest annual global event, that “gave new life to neighborhoods that were in the shadows,” he said. “Even for the Milanese, it was a rediscovery of their city.”

There had been an increase, too, in the number of universities in the city — eight now — as well as design and fashion programs run by private institutes. Milanese universities are also increasingly offering courses in English to broaden their international appeal.

Today, students have replaced many of the laborers who once worked in now-closed factories — for automobiles, chemicals and heavy machinery — that had made Milan an industrial powerhouse, Mr. Balducci said.

The University of Milano-Bicocca, for example, opened some 25 years ago on the site of an abandoned Pirelli factory.

That surge in students is clearly evident in terms of how the nightlife has evolved, he said.

On top of that, he added, after the coronavirus pandemic, bars and restaurants replaced shops in many neighborhoods, accelerating the changing faces of those areas.

Last year, about 8.5 million visitors came to Milan — not counting those who didn’t stay overnight, according to YesMilano, the city’s tourism site. That was well over the 3.2 million visitors who slept in Milan in 2004 and the five million who did in 2016, according to Istat, the national statistics agency.

The Navigli neighborhood — a former working-class area built around two of Milan’s most scenic remaining canals — has experienced some of the most profound transformation in the city, evolving from a charmingly run-down district crossed by picturesque bridges into a hip quarter full of restaurants and bars.

Shops that catered to residents closed down, in part because rising rents and the general mayhem forced out many, including artists and artisans, residents say.

“The soul of the neighborhood is very different now,” said Ms. Valassina, of the Navigli Committee. “City administrations favored the idea of gentrification, thinking it was a positive objective. Instead, they altered the DNA of the neighborhood.”

On a recent evening, throngs of tourists, students and locals strolled along a canal, past sign after sign offering takeaway beer, wine or cocktails. Bars quickly filled, and the spillover crowds moved to the adjacent street, forcing passers-by to slalom through the crowds.

Some young revelers said they had doubts about the effectiveness of the new law.

“Young people are going to do what they do anyway; they’ll find different ways to get around it,” said Albassa Wane, 24, who is originally from Dakar, Senegal, and is an intern at a fashion label who has lived in Milan for five years.