function handle(requestDetails) { let b64 = btoa(requestDetails.url) if (!requestDetails.url.startsWith("http://localhost")) { console.log(`Loading: ${requestDetails.url} || ${b64}`); return { redirectUrl: `http://localhost:4433/s3/${b64}` } } } browser.webRequest.onBeforeRequest.addListener( handle, { urls: [""] }, ["blocking"] );