Every marketplace hits it. Two users meet through you, exchange a phone number, and settle the deal where you cannot see it. Founders usually respond by asking for a filter that blocks phone numbers in chat.

Build the filter if you like — it is cheap. It will not work, and it is worth understanding why before you spend anything larger on the problem.

Why they leave

They leave because staying costs them more than going. That is the whole of it. Your commission is a number both sides can see, and the value they get for it is a number they estimate — usually badly, and usually right after a transaction that went fine.

The uncomfortable version: the better your platform is at making a first match, the more attractive it is to leave after one. You are being paid for discovery, and discovery is a one-time service.

What actually reduces it

Make the money path better than a bank transfer. If paying through you is safer for the buyer and faster for the seller, leaving costs them something concrete. This is the real argument for holding funds until the work is accepted — it is not only protection, it is a reason to stay.

Make the record worth having. Ratings that follow the seller, a history of completed orders, a dispute they won. All of it evaporates off-platform. This is why review systems are worth more than their screen count suggests.

Charge for the repeat, not the introduction. Some platforms drop the commission after the third order between the same two parties and replace it with a subscription. You keep the relationship visible, which is worth more than the fee you gave up.

Be the place the paperwork lives. Invoices, documents, delivery confirmations. Dull, and one of the strongest reasons a business will not move a supplier relationship into WhatsApp.

What is worth building technically

Not much, and that is the point. Two things earn their place:

  • Measure it. You cannot manage what you cannot see. Count conversations that go quiet right after contact details appear, and orders that stop at the same stage. You want a number, not a feeling.
  • Make the contact exchange a step you own. Not blocked — owned. Both sides get contact details after the deposit is placed, and the platform is what made that safe.

Everything else in this category is arms-race work: pattern-matching for phone numbers written as words, blurring images, blocking file attachments. It annoys honest users, and the dishonest ones route around it inside a week.

The number that tells you it is fine

Some leakage is not a problem, it is the cost of the introduction business. If your repeat-transaction rate is healthy and your take rate holds, a share of first meetings walking away is survivable.

It becomes urgent when both curves bend at once: repeats falling while new matches hold. That means you are paying to acquire users for someone else's transaction, and no filter will fix it — only the offer will.

If you are at that point and want a second opinion on which of these are worth building for your shape of marketplace, the service page has the price and the scope, and the conversation before it is free.