Open-source Bullseye is a powerful Windows application designed to evaluate Facebook Marketplace listings by scoring them against real eBay sold-comparison data. It utilizes a deterministic, percentile-rank scoring system that includes confidence intervals, ensuring users have a reliable tool for assessing marketplace deals. While the application is free forever for up to three saved searches, a Pro version is available for unlimited searches and instant alerts.

Key Features

• Real eBay Comparison Data: Bullseye fetches median sales data from the eBay Browse API for listings sold in the past 90 days, giving users a true market comparison rather than just estimates.
• Deterministic Scoring System: Every listing is assessed consistently using a straightforward mathematical calculation, ensuring the same results are produced each time.
• No Facebook Login Required: The application can read public listings without needing a Facebook account, which eliminates the chance of bans associated with unauthorized logins.
• Adaptive Scanning: The app features a four-layer adaptive scanner that adjusts its polling cadence based on user activity to optimize efficiency and resource usage.
• Real-time Scoring: Users can enter a listing and instantly see how it scores against real-time market data, enhancing decision-making for purchases.

How Scoring Works

Scoring is based on the percentile rank within the distribution of similar sold listings. For example:

score = (1 - percentile_rank) * 100

A score of 80 indicates that the listing is cheaper than 80% of comparable sold items, while a score at the median would correspond to a score of 50.

Free vs Pro Plans

Tech Stack

The application is built using a robust tech stack:

• Desktop App: Developed in Python using Flask and SQLite for local storage.
• Cloud Functions: Operates on Supabase for data management and cloud functionality.
• Polling Mechanism: The scraping system runs on the user's machine, safeguarding against Facebook IP bans by polling from the user's home IP address.

Installation

Users can easily download the application through the provided link, with instructions available for verifying the integrity of the downloaded file. Bullseye is currently available as a Windows installer, with plans for macOS support in the future.

For those interested in contributing or building from source, detailed instructions are provided within the repository.