What is it?
What it is
A tiny, fast browser engine written in Rust that renders HTML, CSS, JavaScript, SVG, and images to either a PNG file or a live interactive window.
Why it exists
To provide a lightweight, high-performance browser engine that is not a wrapper around existing engines like WebKit or Chromium, designed for both standalone use and programmatic embedding in game engines or GUI toolkits.
Who should use it
Game developers looking to embed a lightweight browser engine for UI/HUDGUI toolkit developers needing a rendering componentDevelopers building headless browser tools for PNG snapshotsRust developers interested in studying custom browser engine architecturesEngineers needing a lightweight, low-memory footprint web renderer
Who should avoid it
Users requiring full WebGL/Video/DRM support (currently stubs)Developers needing high-performance asynchronous JS (fetch is currently blocking)Users requiring strict security enforcement (SOP/CSP/Sandbox are implemented but not yet enforced in the renderer)Production-critical applications requiring full WHATWG/W3C spec compliance
How it works
A quick walkthrough in plain English
How Falco works
Step 1 of 3
You interact with it
Open Falco, send a request, or connect it to your stack.
Features
Advantages
- Extremely lightweight (~10 MB binary size)
- High performance due to Rust implementation and JIT tier-up
- Minimal dependencies (hand-written PNG encoder)
- Embeddable in game engines (e.g., Bevy, Fyrox) via raw pixel buffers
- Low CPU usage through incremental repainting in interactive mode
Disadvantages
- Early stage development (v0.1.0/v0.2.0/v0.3.0 milestones)
- Many spec-compliant modules (HTML5, DOM, CSS, Security) are implemented but not yet wired into the main renderer
- JavaScript fetch() is currently blocking rather than truly asynchronous
- Limited platform support for JIT (Linux x86_64 only)
- Missing advanced features like CSS animations, transitions, and WebGL/Video rendering
Installation
native
cargo build --release ./target/release/falco page.html --out page.png --width 1200 ./target/release/falco https://example.com --out example.png --width 800 ./target/release/falco page.html --window ./target/release/falco README.html --css style.css --out readme.png
FAQ
What is Falco and what makes it unique?
Falco is a tiny, fast browser engine written entirely in Rust from scratch. It parses HTML, applies CSS, executes JavaScript, and renders to a PNG or interactive window without relying on existing engines like WebKit or Chromium.
Is Falco production-ready?
No, Falco is in an early stage (v0.1.0) and is not production-ready. Many features are stubs or not yet integrated into the render pipeline.
How do I start using Falco?
You can build Falco with `cargo build --release` and then render HTML files or URLs to PNG using commands like `./falco page.html --out output.png` or open an interactive window with `--window`.
What features does Falco support?
Falco supports HTML5 parsing, CSS3 features (including Flexbox, Grid, and Selectors Level 4), JavaScript (with a custom VM), SVG rendering, image loading, and interactive window mode with forms and navigation.
What are the current limitations of Falco?
Falco lacks features like CSS animations, real DOM mutation from JavaScript, full HTTP/2 support, and security enforcement (SOP, CSP) in the renderer. The spec-compliant parsers are not yet integrated.
Can JavaScript manipulate the DOM in Falco?
Yes, as of v0.2.0, JavaScript can mutate the DOM. Changes made via `innerHTML`, `style`, or DOM methods trigger a re-render, allowing dynamic content updates.
Featured in Videos
YouTube tutorials and walkthroughs for Falco
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