# Shadow APIs Every website an agent visits is already an API; the browser is just the client. When a page loads or a button is clicked, the browser issues structured requests to the site's own backend and renders the responses. Those requests are the shadow API: a real, working interface that exists whether or not the site documents one. A browser-first agent ignores this layer and re-derives the same outcome through the visible page every time. The published paper's argument is that internal APIs are all you need: most agent web tasks reduce to a request the browser was already going to make, so an agent that learns that request can skip the interface. This reframes web automation from "control a browser" to "discover and reuse the request behind the browser." Shadow APIs are per-site and undocumented, which is why they have to be discovered from real use rather than looked up. How discovered routes are stored and kept useful is the subject of the next pages. The deeper extraction mechanics are described at the paper's level of abstraction and not below it. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.unbrowse.ai/concepts/shadow-apis.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.