Page Highlighter (MV2) od Matteo Dawson

This add-on provides a fast, privacy-respecting way to visually emphasize content while reading or presenting. Select any text and click the toolbar button to wrap it with a subtle highlight that keeps the original formatting intact. If you click with no selection, the entire page is softly tinted to focus attention without being distracting. The default color is a warm yellow and can be customized from the Options page.
The extension follows a minimal-permissions model. It does not request access to all websites. Instead it uses the active tab permission and injects its content script only after you click the button. All processing occurs locally in your browser. There is no remote code, no analytics, and no network access. The code avoids unsafe patterns such as inline scripts or eval and adheres to Firefox’s content security recommendations for extension pages.