Snapchat wants to know how old you are and help you celebrate it. A new feature called Birthday Party gives users and their friends access to a special lens on their birthday — but only if they choose to share their age with the mobile storytelling app.

The birthday lens is a sticker reading “Happy Birthday” and falling confetti that users can add to a selfie or another image. They can then share that image with their friends or post it to their Snapchat Story. Additionally, on a user’s birthday, a cake emoji will appear next to his or her name, and a user’s friends also will have access to the birthday lens by clicking on that emoji.

Also on his or her birthday, a Snapchat user can tap on the photo filter that traditional displays the time to change it to show the day’s date.

It all sounds like more fun and games on Snapchat, an app that is known for its popularity with millennials, yet the system also encourages users to share their real birthday with Snapchat.

This data point provides valuable information to advertisers and marketers who can target their campaigns to particular ages as well as understand more about Snapchat’s audience.

“Information and data is power. What people need to remember is every piece of data a brand is able to attain from you is another means for them to utilize that data to target you,” Ian Chee, chief strategy officer of MRY, a global marketing agency, wrote in an email.

Snapchat has long claimed that the app is the “best way to reach 13 to 34 year-olds,” as displayed at the top of its advertising page. An estimated 86 percent of Snapchat’s monthly users are between the ages of 13 and 34, according to Snapchat’s internal data.

snapchat graph Snapchat provides the young audience that advertisers and brands crave to find. Photo: Snapchat

But Snapchat's internal data does not directly capture the age of every user. Snapchat has been around since 2011, yet it only started requiring users to enter their birthdays in June 2013. Any user can add her or his birthday by going to Settings and tapping on Birthday. With this update, Snapchat has a new support page on its website that explains those steps.

Still, Snapchat may have the majority of its active users birthdays already. Snapchat had 200 million monthly pics and video sent per day, AllThingsD reported in June 2013. Snapchat now claims more than 7 billion video views per day. The company did not shared a number of active users back then, but now it claims more than 100 million daily active users.

Snapchat has been clear to its users that this data on age can be shared with advertisers. “We personalize the services by, among other things, suggesting friends or profile information or providing advertisements, content, or features that match user profiles, interests, or previous activities,” Snapchat’s Privacy Policy reads.

Users of all social networks at this point are aware that the price they're paying for free services is personal information. “The old media model, consumers paid with time for their content, watch a tv ad, get a free show. Today we pay with time and data,” Chee of MRY wrote in an email.

Regardless of how Snapchat uses the additional data, it would be valuable to advertisers. "If Snapchat starts asking for birthdays it will definitely affect advertising — likely for the better. More tailored messages leading to stronger response rates," said Michael Bruckstein, group planning director at Neo@Ogilvy.

Facebook has long had access to users’ birthdays. On Monday, Facebook added a new birthday feature called the birthday cam. Twitter, a nearly 10-year-old site, introduced a birthday celebration feature in July 2015.