Control which hostnames Browser Run sessions can access

Browser Run now supports guardrails, which limit a browser session's HTTP and HTTPS requests to permitted hostnames.

Use guardrails when you need to:

• Keep a browser workflow limited to a specific website and its subdomains.
• Load only known third-party APIs, scripts, images, and fonts.
• Generate a screenshot or PDF from HTML you provide while preventing it from loading external content.

Set guardrails when starting a session with Puppeteer, Playwright, or the REST API. With a browser binding named MYBROWSER, pass guardrails when launching Puppeteer:

import puppeteer from "@cloudflare/puppeteer"; export async function startGuardedSession(env) { return puppeteer.launch(env.MYBROWSER, { guardrails: { allowedDomains: ["example.com", "*.example.com"], }, }); }

import puppeteer from "@cloudflare/puppeteer"; interface Env { MYBROWSER: Fetcher; } export async function startGuardedSession(env: Env) { return puppeteer.launch(env.MYBROWSER, { guardrails: { allowedDomains: ["example.com", "*.example.com"], }, }); }

In addition to session guardrails, Browser Run now supports a read-only mode for Live View. Live View lets you watch and interact with an active Browser Run session in real time. A read-only link lets someone watch without clicking, typing, navigating, or running JavaScript.

To create a read-only link, set { mode: "readonly" } when generating the Live View URL. This setting affects only the person using that link. The session's hostname restrictions remain unchanged.

Refer to the guardrails documentation for more information.