Adult only. Private by design.
What checking in everyone does

The button checks in eligible guests together. It skips a no-show and anyone unfinished.
The short answer
Check in all eligible guests is a button on the arrival list. Your host invites friends. The host invites friends they'd love to have there. One private link per couple. The note that comes back says eligible guests checked in.
The button shows when check-in is open. On a key party or a play party, check-in opens on party day, after answers lock. A test party can show the list before that.
Adult only. Private by design. You confirm you are 18 or older. The host still checks you in. A private no stays private.
Who the button includes
On a key party or a play party, a couple is included only when that couple is finished. Finished means joined, every card answered, the yes count met, and the profile filled. Both partners have to be finished. If one is short, the couple is left off, and the button does not check in one partner alone. On an open party, a single counts on their own.
A no-show is left off. This button does not undo a no-show. The no-show override is a different control.
On a speed date, each guest who has joined is included on their own. Joined means they saved a profile. A no-show is still left off.
What the button is not
Guests cannot check themselves in. The host checks guests in. A co-host can press the button from the dashboard. They still cannot delete the party or remove the original host.
It is not the door code. The code checks in one person from their phone. This button is the eligible list, all at once. It does not open the cards, and it does not start the reveal.
A night in St. Louis can use the button. New Orleans can too. Those cities have their own pages. The arrival list still lives on the party.
Check-in is not the reveal
All mutual-yes matches are revealed by the format the host already chose. Checking people in does not reveal them. A one-sided yes stays hidden.
A key party shows one Play Partner at the same time, after the host starts the reveal. A play party keeps matches hidden until the host reveals them. A speed date is short rounds, then yes or no.
FAQ
Who gets skipped?
A no-show is skipped. On a key party or a play party, a couple that is not finished is skipped too.
Can one partner be checked in alone?
Not on a key party or a play party, if the other partner is unfinished. The couple is left off. A speed date includes each joined guest on their own. On an open party, a single counts alone.
Can a guest press it?
No. The host checks guests in. A co-host can press it from the dashboard. A guest cannot.
Is this the door code?
No. The door code checks in one person. This button marks the eligible list at once.
When do matches show?
All mutual-yes matches are revealed by the format. A key party shows one Play Partner at the same time, after the host starts the reveal. A play party keeps matches hidden until the host reveals them. A speed date is short rounds, then yes or no.