This morning, when millions of people woke up and swiped their phone opens and tapped on Facebook, they found one of the most important prompts it has ever sent to its users: a link to register to vote or share that you have already done so. Facebook is linking its users to Vote.gov, the mobile-friendly website that the U.S. Digital Service built this past year that links people to online voter registration, in the states that offer it, and to resources for mail or in-person registration for states that do not.

As Politico reported:

Facebook is using its News Feed to steer people on its platform to register for the November election. Today, the tech company launched posts which run through Monday to remind people across the country to register through vote.usa.gov. After completing their registration, people can let their friends on Facebook know that they are registered and encourage them to register too. Facebook’s registration reminders add to its suite of voter features, which has included Election Day reminders since 2008. The reminders will go out to those on the social network who are 18 and up, which with its broad popularity could mean significant spikes in registration nationwide.

Facebook is also hosting an unprecedented service, as Jessica McKenzie reports at Civicist, the Fight for the Future Education Fund has “built a chatbot called HelloVote that can register Americans to vote via SMS or Facebook messenger, both firsts in digital voter registration efforts. Separately, Snapchat announced a voter registration feature, leveraging TurboVote’s technology.

Facebook’s choice to add this civic feature is already impacting traffic to Vote.gov. Thanks to 18F, the public can use Analytics.usa.gov to see that Vote.usa,gov was the most popular federal webpage this morning and has continued to be when this post was written, with thousands of people on the page at the same moment. This is what public-private collaboration looks like in the 21st century.

What’s less obvious is the prompt’s impact on registration, but we can guess that it will be significant: During a two-day push by Facebook this summer, almost 200,000 people registered to vote or updated their records in California.

Facebook, Snapchat the U.S. Digital Service, the General Services Administration and state election officials around the country need to be transparent about who sees this prompt, where, when and the outcomes from it. It matters. To state the obvious, the world’s largest social network can influence elections by prompting its young users to register and get out to vote. Prompts go out, as far as we know, to Facebook users of all ages in the U.S., but young people’s accounts who are highly engaged seem likely to see this more. The technology companies, federal government and secretaries of state need to be open and accountable about what’s coming out of these efforts to ensure that all Americans are being equitably engaged.