Facebook (Nasdaq: FB) is loosening rules to let teens share their content publicly, as the world’s largest social-networking service looks to woo younger members and stave off competition.

While users aged 13 to 17 previously could only share posts as widely as “friends of friends,” they now can make a message or photo available to anyone on the service or across the web, the company said in a post Wednesday. At the same time, Facebook will make “friends” the first option for teens sharing items when they join the site, more restrictive than the previous “friends of friends” preset alternative.

The Facebook blog reads:

“On Facebook, you control who you share with. That can be a single person in a message, a small group, with friends, or with the world.

“Each time you share a status update, you choose the audience you want to share with. Unless you change it, the audience remains the same for future posts.

“Up until today, for people aged 13 through 17, the initial audience of their first post on Facebook was set to “Friends of Friends” – with the option to change it.

“Going forward, when people aged 13 through 17 sign up for an account on Facebook, the initial audience of their first post will be set to a narrower audience of Friends.”

Facebook is seeking to keep younger users engaged on the service as it faces competition for the attention of teens, who are often early adopters of new social-media technologies and have spurred the rise of startups including Snapchat, which lets messages or photos that are sent disappear quickly. Facebook last year bought mobile photo-sharing service Instagram, which had become popular with teens.

“Teens are among the savviest people using social media, and whether it comes to civic engagement, activism, or their thoughts on a new movie, they want to be heard,” Facebook said on its site. “While only a small fraction of teens using Facebook might choose to post publicly, this update now gives them the choice to share more broadly, just like on other social-media services.”

Privacy Firestorm

The changes come amid rising concerns over safety and privacy for children when they interact online. Privacy groups have criticized proposed policy updates at Facebook that said minors would need to verify that a parent or guardian consented to their data being part of promotions.

Other Internet services are also courting younger users. Twitter Inc., which lets users post short messages, lets teens share broadly on its service, along with Google’s own social feature, Google+. Other sites to open up to teens include LinkedIn Corp., a service focused on business users. In August, LinkedIn said users as young as 13 could join in some countries, though it restricted how widely some items — including birth dates and profile photos — can be shared.

As part of the Facebook changes, teens can select an option to let others “follow” them, the company said. This feature, similar to Twitter’s, lets followers easily see posts that are made public.

“In addition, teens will be able to turn on Follow so that their public posts can be seen in people’s News Feeds,” Facebook said. “As always, followers can only see posts they are in the audience for.

“These changes are designed to improve the experience for teens on Facebook. As part of this, we are also looking at ways to improve the way teens use messages and connect with people they may know.”

Facebook said it will add extra steps that tell teens that public posts can be seen by anyone if they select the option.

“We take the safety of teens very seriously, so they will see an extra reminder before they can share publicly,” the company said.

Facebook has made other efforts around online safety. Earlier this year, the Menlo Park, California-based company partnered with the National Association of Attorneys General to start a consumer-education program to provide teens and parents with help on how to manage their “privacy and visibility, both on Facebook and more broadly on the Internet.”

The entire Facebook post can be read online.