Cloudflare launches Kitesurf browser for AI agents

Cloudflare has launched Kitesurf, a browser for AI agents that runs on its Workers platform. The product is available in beta through Browser Run.

Kitesurf is designed as a lighter alternative to Chromium for tasks such as taking screenshots and extracting HTML. It prioritises lower CPU and memory use over the full feature set built for human users.

Cloudflare is positioning the release around a growing need for browsers that support automated agents as AI tools take on more web-based work. It argues that conventional browser engines carry overhead many automated tasks do not need, making them costly to run at scale.

Kitesurf runs in V8 isolates on Cloudflare Workers and was built over 12 weeks. The project drew on several parts of the company's developer platform, including WebAssembly support in Workers, Dynamic Workers, SQLite-based Durable Objects, worker-to-worker RPC, service bindings and broader Node.js compatibility.

The browser is offered through Browser Run, Cloudflare's headless browser automation service. Users can access it through the Chrome DevTools Protocol, allowing existing tools such as Puppeteer, Playwright and chrome-remote-interface to connect without major changes.

Built for agents

Cloudflare said the design reflects the needs of software agents rather than people using a browser directly. That meant dropping features such as tabs, themes, browser extensions and device synchronisation, while prioritising machine-readable output, scalability and operating cost.

The security model also differs from that of a consumer browser because agents may be directed at arbitrary websites for specific tasks. Kitesurf was built on the assumption that every page load is untrusted and that each session should start fresh.

Its architecture has three main components: the Engine, PageScript and PageRenderer. The Engine is the public-facing element that handles the protocol connection and stores session state, while the other components remain stateless.

PageScript manages a page session inside a separate isolate, including the global environment and document object. For HTML and CSS parsing, Kitesurf uses parts of Blitz and Stylo, both written in Rust, while a separate SandboxOutbound worker handles network requests for assets such as images, stylesheets, fonts, JavaScript files and WebAssembly files.

That network access is tightly restricted, with SandboxOutbound as the only component allowed to fetch from the internet. It enforces CORS, injects browser-style headers, filters responses and isolates cookies for each page.

Performance trade-offs

Cloudflare said Kitesurf already passes more than 215,000 Web Platform Tests. It also reported comparative results against Chromium across a 14-URL test set, showing lower CPU and memory use but slower overall completion times.

For screenshots, Kitesurf used 380 milliseconds of CPU time versus 1,173 milliseconds for Chromium, and 57.8 MiB of memory versus 271.0 MiB. For HTML extraction, it used 229 milliseconds of CPU time versus 877 milliseconds for Chromium, and 39.4 MiB of memory versus 273.7 MiB.

Wall time moved in the other direction. Kitesurf took 1,148 milliseconds for screenshots versus 637 milliseconds for Chromium, and 820 milliseconds for HTML extraction versus 472 milliseconds for Chromium.

Cloudflare attributed that trade-off to Chromium's just-in-time compiler and mature rendering stack, while Kitesurf currently relies on a cold software renderer. Even so, it argued that lower memory and CPU use matter more for cost-sensitive automated workloads.

Current limits

Cloudflare said the browser already renders sites including Wikipedia, Hacker News, the Cloudflare Blog and parts of the Cloudflare dashboard, as well as several TodoMVC implementations. It described Kitesurf as suitable for one-shot jobs such as content extraction, PDF generation and screenshots on compatible sites.

At the same time, the browser is not yet intended for use cases that need video playback, WebGL rendering, long authenticated sessions with persistent state, or bot-challenge handshakes tied to real TLS fingerprints. In those cases, Browser Run's default Chromium option remains the recommended route.

The engineering team also highlighted several design choices behind the product, including extensive use of automated testing and a preference for Rust compiled directly to WebAssembly. Cloudflare said this helped it avoid heavier emulation layers and keep the browser more compact.

One technical workaround involved handling eval operations. Because Workers do not natively support eval in the way this browser design requires, Cloudflare used Boa JS, an ECMAScript engine written in Rust, to compile and run those operations inside Workers.

Cloudflare plans to expand support for the Chrome DevTools Protocol, improve rendering fidelity and continue increasing Web Platform Tests coverage. It also intends to open source Kitesurf once it is ready so customers can deploy their own version on their Workers accounts.

Cloudflare summed up one milestone in simpler terms: Kitesurf runs Doom.