onUI is a versatile Chrome add-on designed for annotating UI elements directly on live web pages, making it ideal for developers and designers looking to address UI issues. With no code integration required, users can easily mark single or multiple elements, adding intent and severity metadata to each annotation. The tool allows for flexible reporting options, including compact, standard, detailed, and forensic formats, enhancing the workflow of UI debugging and AI-assisted development.

This add-on supports tab-scoped annotations, enabling users to control visibility per tab, and it can sync with a local MCP bridge for more advanced workflows in AI environments. onUI is built with a local-first approach, ensuring that users can manage annotations and reports without the need for backend infrastructure, streamlining the process of iterative UI debugging and AI pair-programming.