The new rules reduce the expensive bureaucratic hurdles long faced by Cubans wishing to go overseas, many of whom know loved ones who lost everything when they emigrated or who left the island in the dead of night on rafts and powerboats.

As of Monday, most Cubans can head for the airport with only a passport, a plane ticket and a visa, if required, from the country they intend to visit.

“We have lived for decades in captivity,” said Marta Rodríguez, 65, a retired office manager who was waiting to pick up a tourist visa from the United States Interests Section in Havana. “It’s a positive move — one they should have taken 50 years ago.”

The change is not expected to prompt a major exodus, because most countries use entrance visas to control the number of visiting Cubans, and international travel remains way beyond the means of most islanders, who earn state salaries of about $20 per month. There are, of course, Cubans who want to travel from the island and return.

The government says it will continue to limit travel for tens of thousands of Cubans who work in strategic sectors, like military personnel and scientific workers, as well as those they deem a threat to national security.

How tightly, and for how long, the government will continue to control those sectors’ movements will become apparent only over time, Cubans and outside analysts said. In a development that could signal new government flexibility, Yoani Sánchez, a prominent blogger and activist who says she has been denied an exit visa by the Cuban government at least 19 times in the past, said on Monday that she was one of the first in line at the immigration office and submitted paperwork for a new passport without any problems.

Arturo López-Levy, a Cuban-born academic who left the island 10 years ago and lectures at the University of Denver, said the migration reform was not simply a maneuver to defuse political pressure but a structural shift in the relationship between the island and the diaspora — a community that the government once rejected as traitorous “worms.”

“This is a real change in the way in which the government perceives the relationship between the Cuban population and the outside world,” he said.

At immigration offices, Cubans scrutinized posters clarifying the new rules, stood in line to get new passports and pressed around immigration officials in spearmint-color uniforms seeking details of what paperwork was now required.

More police officers were on hand than usual outside immigration offices and near consular offices, particularly the small park near the United States Interests Section — known locally as “the place between life and death” — where Cubans wait each day for appointments with American consular officers.

The Obama administration was watching the developments with interest. “We will see if this is implemented in a very open way and if it means that all Cubans can travel,” said Roberta S. Jacobson, assistant secretary of state for Western Hemisphere affairs, according to The Associated Press.

Despite multiple reports in recent weeks by official Cuban news media, many Cubans seemed unclear about how the new law would work: whether it applied to them, whether they needed a new passport or a special stamp (they do not), how it would work for minors.

Under the old system, most Cubans who applied for an exit permit to travel received it — if they could provide the authorities with an invitation letter from someone in the country they intended to visit — all at a cost of nearly $400.

Caridad Reyes Risse, 69, a retiree who was in line at a downtown travel agency to buy a ticket to visit her daughter in the United States, said she had waited until Monday to avoid that $400 expense.

“The question now is, ‘Will I get a ticket?’ ” she said, gesturing to the gaggles of Cubans that spilled out of the tiny agency.

Ramona María Moreno, 61, a restaurant worker, said that even though most Cubans who sought permission in the past received it, the change had psychological importance.

“It’s the idea you can go,” said Ms. Moreno, who was at an immigration office looking for a list of countries that admit Cubans without a visa. “It’s a freedom that we have never had.”

She acknowledged there were still barriers to travel. “I have no money,” she said with a chuckle.

The news last week that the government would allow members of its jealously guarded medical corps to travel has prompted excitement among doctors who for decades have had to go through a lengthy process to get permission, if they got it at all.

“Everyone is waiting to see what happens,” said Niurka, 45, a doctor who would like to join her family in Miami. Requesting that her last name not be published to avoid riling the authorities, she said she did not believe the tight restrictions on medical professionals would be lifted overnight.

“Still, it gives me hope,” she said.

However the government chose to carry out the new regulations, they signified a new era in Cuba’s relationship with its diaspora and the wider world, said Ms. Rodríguez, the retiree.

“They have realized the island needs to open up to the world,” she said “They can’t go back on this now.”