For those concerned about loved ones, or those in Paris wishing to assure friends and family of their whereabouts, Facebook launched a feature allowing users to let their network know they are safe.

As President François Hollande urged those in the city to shelter, the hashtag #porteouverte allowed users to find Parisiens willing to open their homes to provide refuge for those in need. The hashtag continued to trend as further flights were canceled Saturday, and many remained stranded in the city.

Meanwhile across social media there were reports of taxis turning off their meters to help people get home for free.

The sentiments #prayforparis and #peaceforparis rippled across Twitter, many accompanied by a poignant image of the Eiffel Tower in a CND symbol.

Buildings around the world, including the Empire State Building in New York, Wembley Stadium in London and Rio de Janeiro’s “Cristo Redentor” statue lit up Friday night in France’s national colors of red, white and blue to show their solidarity with the victims and the city of Paris.

Taylor Swift tweeted “Look for the helpers,” a sentiment that echoed across social media.

Facebook activates ‘Safety Check’

Ways to donate

Several organizations responded across the city in the aftermath of the attacks:

The French Red Cross mobilized over 300 volunteers to help those impacted. You can donate here.

And even while urged to remain inside, people across Paris lined up to give blood at donation centers and hospitals. Those in the area can access a map of blood donation centers using the Don du sang app here.

Another organization whose roots are in France is Médecins Sans Frontières, or Doctors Without Borders. You can donate to their work in France and around the world here.

The French Interior Ministry launched a website to report those missing, as well as take evidence, here.

Americans in Paris were urged to call 001 202 501 4444 for information and assistance. Those in the U.S. concerned about loved ones in Paris should call 1 888 407 4747.

Complete coverage on the Paris attacks