Cloudflare Open-Sources Kitesurf, a Chromium-Free Browser for AI Agents

Cloudflare published the source code of Kitesurf, its browser engine for AI agents, on GitHub under the Apache 2.0 license on Nov. 13. The release fulfills a promise the company made when it launched the engine in August. It is an open-sourcing, not a finished product, and Cloudflare itself labels the project "an experimental browser engine."

The engine runs entirely on Cloudflare Workers, with no Chromium process and no browser container. It speaks the Chrome DevTools Protocol, so existing automation clients such as Puppeteer can connect to it, and Cloudflare says AI agent harnesses can point at the same CDP port, according to the company's blog post and the project's GitHub page.

What is actually in the repository?

Kitesurf parses HTML, applies CSS, runs page JavaScript and renders screenshots without Chrome. The code is assembled from existing open-source Rust packages compiled to WebAssembly:

• Blitz handles HTML parsing, the DOM, layout and painting.
• Stylo, the CSS engine taken from Firefox, handles styles.
• Boa runs JavaScript inside WebAssembly, as a fallback when page scripts cannot run in Dynamic Workers.
• Linebender libraries provide text layout and 2D graphics.
• Krilla produces PDFs.

Cloudflare splits the engine into three components. An Engine manages sessions and client connections. PageScript runs the page and its JavaScript. PageRenderer draws the result.

Self-hosting is not free in either sense. Kitesurf uses Dynamic Workers to create an isolated Worker for each page, so deployment requires a Workers Paid plan. Local development runs only through Cloudflare's wrangler tool. The engine is open, but the economics still route through Cloudflare's platform.

Why build a browser without Chromium?

The company's pitch is cost and scale. At launch, Cloudflare engineers argued that Chromium's memory and compute requirements make a dedicated browser per agent too expensive, according to InfoQ. They described Kitesurf as "an ephemeral, fully-isolated, stateless engine designed to exist only for the duration of a task."

The trade-off is compatibility, and it is a large one. Kitesurf does not support video, WebGL, TLS-fingerprint bot challenges or long-lived authenticated sessions, Cloudflare confirmed on Nov. 13. The company states plainly that the engine is not meant to replace Chromium. Any agent workflow that touches streaming media, 3D graphics or persistent logins falls outside its reach.

Can outsiders contribute?

When Kitesurf launched in August, Hacker News commenters questioned whether a company that sells anti-bot protection should also sell a browser for bots, and Reddit users asked why the code was closed, InfoQ reported. The Nov. 13 release answers the second criticism, at least formally.

In practice, contribution is gated. Cloudflare says outside contributors must open an issue and be vouched for by a maintainer before submitting a pull request. The company also warns that the engine is "under heavy development," which sets expectations for anyone building on it.

There is a partial transparency mechanism. Cloudflare tracks the engine's Web Platform Tests scores and benchmarks on its kitesurf.dev landing page. Those numbers will show, over time, how far the engine stands from real browser behavior.

For developers, the immediate value is limited but real: read the code, run it locally, modify it, deploy a private instance instead of using Cloudflare's managed Browser Rendering service. What Kitesurf cannot yet do — video, WebGL, durable sessions — defines its boundary as sharply as its license defines its openness, and Cloudflare's own test score tracking will determine whether the gap closes.