CarMax Web Trade-In Estimate Overlay

WHAT IT DOES

CarMax Web Trade-In Estimate Overlay reads vehicle price and details from CarMax listing pages and displays a floating estimate overlay showing the estimated trade-in value of the vehicle. The overlay shows the vehicle name, listing price, estimated trade-in value, and a comparison between the two values with a percentage difference. A color-coded indicator—green for favorable or yellow for neutral—helps you quickly assess the trade-in value relative to the listing price. A "Get Full Estimate" button opens the CarMax trade-in estimator page. The extension stores vehicle history per vehicle, tracking how many times you've viewed each listing, the last listing price, and the last estimated trade-in value. The overlay is fully draggable, resizable, and remembers its position, size, and opacity across sessions.

WHERE IT RUNS

This extension works on all CarMax pages at carmax.com and its subdomains, specifically on vehicle listing and detail pages. It runs on the main vehicle view, the search results page, and any page displaying vehicle pricing information. The extension operates entirely within your browser and does not access CarMax's servers directly—it reads only what is visible on the page you are viewing. It works alongside the free BotGentz extension, which provides the necessary scripting environment.

HOW TO USE

Install the extension, then navigate to carmax.com and open any vehicle listing. The extension automatically creates a floating trade-in estimate overlay on the page. Click the extension's icon in your browser toolbar to open the settings panel. Use the "Show Overlay" / "Hide Overlay" button to toggle visibility. The overlay shows the vehicle name, listing price, estimated trade-in value, and a comparison percentage. Click the "Get Full Estimate" button to open the CarMax trade-in estimator page for a more detailed evaluation. Adjust the overlay transparency using the opacity dropdown (70%, 82%, 92%, or 100%). The "Refresh" button manually updates the overlay with the latest vehicle information. Drag the overlay by clicking and holding anywhere inside it. Resize it by dragging the bottom-right corner. Close the overlay with the × button.

AGE AND DEPRECIATION-BASED ESTIMATION WITH PER-VEHICLE TRACKING

Unlike simple percentage calculators, this extension uses a multi-factor estimation model that considers vehicle age and mileage. The estimate is calculated using the listing price multiplied by a base trade-in factor (78%), adjusted by an age depreciation factor that reduces value by 8% per year of vehicle age, and further adjusted by a mileage factor based on average annual mileage (12,000 miles per year). The extension also tracks per-vehicle history using a unique identifier derived from the vehicle's VIN or listing name. This history includes view count, last listing price, and the last estimated trade-in value, allowing users to track value changes over time. The comparison indicator shows the percentage difference between the trade-in estimate and the listing price, helping users quickly assess the vehicle's value proposition.

THE PANEL

The panel supports drag-to-move anywhere on the page. It remembers its position per site, so it stays where you placed it on carmax.com. Click the panel header to collapse it down to just the minimized bubble, or click the expand handle to show the full panel. The panel can be resized by dragging the bottom-right corner. Press the Escape key to close the expanded panel and return to the minimized state. All panel settings, including position, size, collapsed state, opacity, and vehicle history, are saved per site and persist across browsing sessions.

PLEASE NOTE

This extension requires the free BotGentz extension to be installed and active, as it provides the underlying DOM injection and script execution environment. CarMax's website changes periodically, and vehicle element structures, class names, and page layouts may be updated. When that happens, the extension may stop detecting vehicle data until an update is released. The extension stores your overlay position, size, opacity, visibility, and vehicle history locally in your browser's storage using GM_setValue. Vehicle history is stored as a key-value object where keys are vehicle identifiers and values contain view count, last price, and estimate. The trade-in estimate is a rough approximation based on age and price factors—actual trade-in values may vary based on vehicle condition, market conditions, and CarMax's current valuation methods. Always verify with CarMax directly for an accurate assessment. No data is ever sent to any server, and no personal information is collected. You can clear all stored settings at any time by clearing your browser data for carmax.com.