Before You Build
Mobile AppShut Down

Selltag

Selltag was a Spanish peer-to-peer marketplace for buying and selling secondhand and other goods.

View original story

Product snapshot

What it was

Selltag let users publish listings, share product links, negotiate with other users, and support selected cross-city transactions through a delivery feature.

Who it was for

people selling secondhand goodsbuyers browsing used itemssmall sellers listing used, new, handmade, or digital goods

Problem / value

Make buying and selling used, new, handmade, and digital goods easier across web and mobile.

Core workflow

  • create product listings
  • share listing links
  • negotiate with buyers or sellers
  • arrange selected cross-city delivery

Product form

web appiOS appAndroid apppeer-to-peer marketplace

Pricing model

Novobrief reported a Telotransporto delivery feature priced at EUR4.99; the broader monetization model is not fully public.

What happened

Summary

Selltag shut down after downloads and registrations failed to translate into enough buyer retention, marketplace engagement, and sustainable matching against better-funded competitors.

Outcome

Selltag shut down; public sources do not disclose cohort retention, transaction volume, gross merchandise value, or revenue from delivery.

Demand signal

Public sources report strong downloads and registrations, but the CEO identified user engagement, buyer retention, and buyer-seller matching as the hard constraints.

Distribution issue

Selltag faced a crowded mobile marketplace category where paid and organic acquisition were not enough unless dense buyer liquidity already worked.

Timeline

  • Selltag began as a web-based marketplace for used items.
  • The company later shifted to a mobile-first strategy.
  • Novobrief reported more than 250,000 downloads and 55,000 registered users.
  • Novobrief reported that the apps disappeared from iOS and Android stores in October 2015 and would not return.

Before you build

Why it matters

A marketplace can look active while the constrained side, often buyers, is still too weak to keep the loop alive.

Primary check

Prove repeat buyer demand, time-to-match, and transaction completion before treating downloads or seller listings as marketplace traction.

Checklist

  • Measure completed repeat transactions, not just downloads.
  • Track buyer response rates and time-to-match.
  • Validate the harder side of the marketplace first.
  • Use one narrow geography or category before competing broadly.

Relevant if

  • You are building a peer-to-peer marketplace.
  • You have seller supply before buyer demand is proven.
  • You compete with better-funded local marketplace incumbents.
  • You are using a feature such as delivery to differentiate a marketplace.

Less relevant if

  • Your product is a single-sided SaaS with no buyer-seller matching.
  • You already have repeat completed transactions in a narrow market.

If you build this today

Start with one narrow geography or category, measure repeat completed transactions, and only add delivery or broader app features after the liquidity loop is working.