The problem

Most recreational sport groups run on WhatsApp, and every one of them hits the same wall. Someone posts “football Thursday 7pm, first 14 in.” Then come forty messages. Three people say “in” twice. Two drop out in a thread nobody reads to the end. Somebody’s counting on their fingers an hour before kickoff, and the organizer is chasing five-euro payments one DM at a time.

Chat is excellent at conversation and hopeless at state. The roster exists only as a running tally in the organizer’s head.

The approach

The chat is where the group actually lives, and that doesn’t need to change.

So whosin doesn’t replace, it coexists:

• The app owns the structured state: who’s in, capacity, the waitlist, who has paid, what’s on the schedule.
• WhatsApp stays the comms layer: banter, photos, last-minute changes.
• Crossing the gap is one tap: The organizer shares to WhatsApp from the app; players tap a public link and see the live roster without making an account.

That last point matters more than it sounds. Requiring every casual player to sign up is how these tools die. Only the organizers need an account.

One primitive

The three groups I built this for want three different things. One wants players to tap “I’m in.” One wants the organizer to mark people paid via Venmo. One is a fixed team that needs Yes / No / Maybe against a recurring calendar.

The temptation is three features. The abstraction that collapses them: a confirmation takes a slot. What counts as a confirmation is the variable. A player tap, an organizer marking a payment, an RSVP. Payment becomes a layer on top rather than a prerequisite, and the open-event flow ships without waiting on it.

Status Live

Live, with three real groups using it. A fixed roster team and two pick-up groups, spanning the range from most to least structured.