They did so by tweeting #PortesOuvertesNice
which quickly started trending, with local newspaper Nice Matin one of the first to use the hashtag, which was retweeted over 3,000 times.
A number of countries' Foreign Offices also shared the hashtag, as did the Nice Twitter account.
One Twitter user, who has lived in NIce for five years, told CNN -- he didn't want to be identified -- that after tweeting the hashtag six French people in their twenties came to his home for shelter. In the end they only stayed for 10 minutes before heading for the train station to return home.
Art historian Thomas Schlesser, who works at the Hartung-Bergman Foundation in Antibes
-- 20 kilometers away from Nice -- was another to tweet the hashtag.
"When I heard about the attacks and I saw the hashtag I thought it was possible to help," the 38-year-old Schlesser told CNN in a phone interview. "We have four rooms free, and although I didn't have any calls for me this was a message of solidarity. The foundation is a nice place with a lot of space.
"I wanted to put the tweet in English because I thought it was the tourists who were most likely to be in need. But I did not have a call in the night, perhaps because we're 20 kilometers (roughly 12 miles) from the scene of the tragedy."
Schlesser knew Pierre Innocenti and Hyacinthe Koma
, who were killed in the November attacks in Paris, and as he reflected on what had happened on Bastille Day in Nice along the Promenade des Anglais, he insisted he wouldn't be cowed in the way he lived his life.
"Nothing will change my behavior," he added. "I often take the train and the plane and I will not change my daily life. I think about the threat sometimes, but I categorically refused to change my lifestyle. It's certainly easier for someone like me who, at 38, has no children ... Anyway, I'm not afraid."
Law student Cassandra Ferreri, who was born in Nice -- "This is my town," she said -- was another to tweet #PortesOuvertesNice.
"It's a nightmare," said Ferreri, who is studying in Lyon, but comes back to Nice every summer. "The Promenade des Anglais on July 14 is full of people, especially families. When you're 20 and you have to call your friends to know if they're alive -- for the second time in less then a year -- it's terrible.
"My city is beautiful, and instead of pictures of corpses on the Prom, I would like to see on TV the Prom that I know, the one with the blue chairs, the blue sky, and the people walking happily.
"If I responded to the hashtag, it's because it was the only way I can help," added Ferreri, who lives a 15-minute walk away from the Promenade.
Since the Charlie Hebdo attack in January 2015
, the 20-year-old law student believes French youths "live in fear."
"We may all scream 'We are not afraid' and write it on the Place de la République in Paris, but this is just to deny. When I speak with my friends, we all agree that now, we just have to live with that fear.
"After an attacks, we feel numb for a couple of weeks, but then life goes on. I haven't changed anything in my way of life and I still drink outside and go to concerts.
"The only thing that changed for me this night, with this attack, is that I'm going to hug everyone one I know and make the most of them, because it could have been me or my family. I just realize that it can happen anywhere, at any time."