Watch: Node ID
A sequential identifier assigned to each content node during extraction via depth-first traversal. These IDs appear in the structured Markdown output as {#ID} references, enabling the AI to target specific elements on the page for reading, citing, or interaction.
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When Google Chrome extracts the content of a web page, it assigns a sequential identifier to every single node in the rendering tree. As the browser scans the page, it labels each element—one, two, three, and so on.
These numbers, called content node IDs, are then woven directly into the structured Markdown that the Gemini artificial intelligence model receives. For example, a heading might be tagged with ID two, a paragraph with ID four, and a link with ID five.
This simple labeling system is what makes page interaction possible. When Gemini needs to click a button, fill out a form, or follow a link, it simply references the node ID. Chrome then matches that ID back to the actual element on the live page. A built-in matching algorithm even verifies the element's type, position, and interactivity, which keeps things working smoothly even if the webpage changes dynamically.
Behind the scenes, Chrome actually manages two kinds of identifiers. While the content node ID is assigned to every node for Gemini to use, a second identifier—called the DOM node ID—is much more selective. To protect browser performance and keep memory usage low, Chrome only assigns this second ID to elements on a strict allowlist. This list always includes actionable targets like buttons and links, ensuring the browser stays fast while still giving the AI the precise coordinates it needs to navigate the web.