Image Optimisation Checker

WHAT IT DOES

Image Optimisation Checker is a browser extension that scans any webpage for images and checks for common optimisation issues. It checks for missing alt text, missing width and height attributes, missing lazy loading, oversized images, and missing srcset for responsive images. The tool displays a list of all images with their status, highlighting issues in red with specific recommendations for improvement. A summary shows the total number of images and the number of issues found. The tool is ideal for web developers, SEO professionals, content creators, and anyone who wants to ensure images are optimised for performance, accessibility, and user experience.

WHERE IT RUNS

Image Optimisation Checker runs on any webpage, overlaying a floating panel that does not interfere with page content. It operates entirely in your browser as a lightweight userscript, scanning the DOM for image elements. It works on any page, whether static or dynamic, with no external dependencies. All settings are stored locally using GM_setValue—no data is ever sent to any server.

HOW TO USE

After installation, open the floating panel by clicking the extension icon. The panel shows the current status (Enabled or Disabled) and a toggle button to enable or disable the checker. The panel displays a summary with the total number of images and the number of issues found. A list shows each image with its source URL, alt text, dimensions, loading attribute, and natural dimensions. Images with issues are highlighted with a red border and show recommendations for improvement. Click the "Scan Images" button to manually rescan for images. The tool automatically rescans when the page content changes. All settings are saved per website.

REAL MECHANISM — WHY THIS WORKS

Most image optimisation tools require manual inspection of the page source or external tools that may not show the actual page context. Image Optimisation Checker uses a DOM-scanning approach that directly reads image elements from the page. The tool queries the page for all img elements, then checks each one for optimisation issues: alt attribute presence and content, width and height attributes, loading attribute, file size by comparing natural dimensions to display dimensions, and srcset attribute for responsive images. Each image is classified with issues and recommendations. The tool also checks if the image is decorative (alt="" and role="presentation") and handles that case appropriately. Results are displayed with color-coded cards (green for OK, red for issues) and recommendations for each issue. The tool uses a MutationObserver to detect dynamically added images and rescans automatically. This approach ensures accurate, fast, and fully private image optimisation auditing without requiring any external services or network access.

THE PANEL

The floating panel is fully draggable and remembers its position per site, snapping to the edges of the viewport when dragged near them. You can collapse the panel to a small icon to minimize screen distraction and expand it back with a single click. The panel is resizable from the bottom-right corner, giving you more space to view the image list. Press the Escape key to close the panel instantly. The panel remains open across page navigation within the same domain, maintaining your current view state. All preferences—panel position and enabled state—are saved per domain for a seamless experience.

PLEASE NOTE

Image Optimisation Checker requires the free BotGentz extension to be installed and enabled, as it relies on the cross-extension messaging API provided by BotGentz for DOM access permissions. The tool checks for alt text, width/height attributes, lazy loading, and srcset. It does not check image file size directly, but uses natural dimensions vs. display dimensions as a proxy for oversized images. The tool provides recommendations based on common best practices. All settings are stored locally in your browser using GM_setValue. No image data, page content, or usage information is ever sent to any server. The extension does not read, store, or transmit any personal information. It only scans and displays image data at your request.