# Internal hostnames

Cloudflare added internal hostnames to the persistent browser in its Agents SDK: give the browser a name such as preview.internal and requests to it go to the agent itself rather than the internet. The agent can then check a dev server in its sandbox, a folder in its workspace, or another Worker in the same browser it uses for the web, with nothing exposed publicly. Each internal host has a fetch function running in the Durable Object, so it can use that object's bindings and state, and a host can carry a target schema so the model chooses which port or folder it serves.

Cloudflare added internal hostnames to the persistent browser in its Agents SDK: give the browser a name such as preview.internal and requests to it go to the agent itself rather than the internet. The agent can then check a dev server in its sandbox, a folder in its workspace, or another Worker in the same browser it uses for the web, with nothing exposed publicly. Each internal host has a fetch function running in the Durable Object, so it can use that object's bindings and state, and a host can carry a target schema so the model chooses which port or folder it serves.