OfferUp: Buy. Sell. Simple. represents the merged marketplace platform combining OfferUp and Letgo's user bases into a single mobile application for local and national secondhand transactions. The Android application maintains a 4.4-star rating, positioning itself as a modern alternative to traditional classified ads and garage sales for everyday consumers seeking to buy or sell used items. The application's core functionality centers on a streamlined listing process that allows users to photograph items, set prices, and post listings within minutes. The platform supports both local transactions through coordinated meetups and nationwide sales via integrated shipping services. Users can print shipping labels directly through the app, with packaging instructions provided for standardized shipment preparation. The messaging system facilitates communication between buyers and sellers, while the rating system helps establish trust among community members. User experience demonstrates thoughtful design with intuitive navigation and clean interface elements. The search functionality incorporates location-based filtering to show relevant local items, while category organization helps users quickly find furniture, electronics, clothing, or other specific item types. Real-world usage patterns show peak activity during evenings and weekends, with successful transactions often involving quick response times and clear communication between parties. The app's notification system keeps users informed about messages, offers, and item views. User feedback trends highlight satisfaction with transaction simplicity and shipping integration. Ken Heaton's August 29, 2025 review notes appreciation for the service fee structure and streamlined shipping process, stating the instructions make packaging 'simple.' Bruce Miller's August 30, 2025 review praises the 'fair system' that ensures buyers cover shipping costs appropriately. However, some reviews reference occasional payment confusion, as Jeffrey Phillips noted on September 4, 2025 regarding fluctuating service fees, while Kenneth P's September 5, 2025 review acknowledges the challenge of dealing with 'flakes' in the marketplace. The platform demonstrates significant strengths in transaction convenience and integrated shipping solutions, though it faces limitations regarding user reliability and occasional fee transparency issues. Ideal use cases involve selling household items, furniture, or electronics locally, while the shipping functionality expands reach for smaller, shippable goods. The application serves best those willing to navigate occasional communication challenges for the benefit of a large, active user base and streamlined transaction tools.