NFT Cross-Marketplace Price Comparator

WHAT IT DOES

NFT Cross-Marketplace Price Comparator watches the current page for NFT listings, extracts the NFT ID and collection name, then makes parallel requests to multiple marketplace APIs to fetch prices for the same NFT across different platforms, displaying a side-by-side comparison with best price recommendations and savings calculations. The tool helps you find the best deal by comparing prices across marketplaces before making a purchase.

WHERE IT RUNS

This tool works on any webpage that displays NFT listings with IDs and contract addresses, including NFT marketplaces, collection pages, and trading platforms. It automatically detects NFT information from page content and fetches comparative data from supported marketplaces. The script runs on all websites as designated in its match patterns.

HOW TO USE

After installing the BotGentz extension, navigate to any NFT listing page. Click the NFT Cross-Marketplace Price Comparator icon in your browser toolbar or use the keyboard shortcut (Alt+C). The panel will open. Click "Connect Wallet" to connect your real EVM wallet extension—this enables gas price detection for more accurate comparisons. Configure which marketplaces to check by entering comma-separated marketplace keys (opensea, looksrare, rarible, blur, x2y2). Set the check interval in seconds and toggle whether to include fees and gas costs in the comparison. Click "Compare Now" to fetch prices from all enabled marketplaces. The panel displays a side-by-side comparison showing each marketplace's price, with fees and gas included if enabled. The best price is highlighted with a star and savings calculations show how much you would save compared to the current page price.

TECHNICAL SECTION — PARALLEL API FETCHING AND PRICE AGGREGATION ENGINE

Unlike manual price checking across tabs, this tool uses a parallel API fetching and price aggregation engine. It first detects the NFT ID and contract address from the page DOM using multiple strategies. The engine then makes simultaneous API requests to all enabled marketplace endpoints using GM_xmlhttpRequest, handling each response independently to avoid blocking. Each marketplace's price data is parsed from the response, with fallback parsing for different API response structures. The engine then aggregates results and applies user-configurable adjustments including marketplace fees (known percentages per platform) and estimated gas costs. A best-price selection algorithm identifies the lowest total cost, and savings are calculated against the current page price. All results are displayed in a structured, color-coded format with the best option clearly highlighted. This approach provides comprehensive price visibility without requiring manual cross-referencing.

THE PANEL

The panel is draggable anywhere on the screen and remembers its position per site. It can snap to the left, right, top, or bottom edges, or float freely. Collapse it to a small status indicator when you need more page visibility, and expand it again with a single click. Resize it vertically or horizontally to show more comparison results. Press Escape to close the panel instantly. All settings (enabled marketplaces, interval, fee inclusion, gas inclusion) are saved globally and persist across sessions.

PLEASE NOTE

This tool requires the free BotGentz extension and a real EVM wallet extension already installed in your browser. EVM chains only—supports Ethereum Mainnet, Polygon, Arbitrum, and Optimism. Wallet connection is read-only; this tool never initiates transactions or signs messages. Cannot access marketplace data that requires API keys or authentication, cannot fetch prices from marketplaces that block cross-origin requests, cannot compare NFTs that are not listed on multiple marketplaces, and cannot account for marketplace-specific fees that are not publicly documented. Users must manually verify price comparisons before making any purchase decisions. Supported marketplaces: OpenSea, LooksRare, Rarible, Blur, X2Y2. Websites change their layouts frequently; scripts may need updates, and we work to keep them current but cannot guarantee uninterrupted operation.