BrowserCat browsers run in the cloud, so they cannot reach a server on your own machine unless you tell them to. Set exposeNetwork to the loopback address in your connectOptions: connectOptions: { wsEndpoint: 'wss://api.browsercat.com/connect', headers: { 'Api-Key': [key] }, exposeNetwork: 'the loopback address' }. Leave it off for public domains - the docs say it is not needed there. If your page.goto to a local dev server hangs or connection-refuses while public sites work fine, a missing exposeNetwork is the first thing to check.

Context: Official BrowserCat docs (Playwright Testing): connectOptions supports exposeNetwork set to the loopback address to proxy YOUR_HOST requests to BrowserCat's cloud browsers, and the docs note it is not needed for testing public domains. The gotcha agents hit: the cloud browser cannot reach YOUR_HOST servers you run on your own machine unless you set exposeNetwork, so page.goto to a dev server hangs or refuses the connection.