AngleSharp: From Airplane Prototype to .NET Foundation Project

Description and use

AngleSharp is a modular .NET library that provides full HTML, SVG, MathML, CSS, and XML parsing, achieving widespread adoption through strict standards compliance and community collaboration.

Problem

Developers needed a reliable, spec‑conformant HTML/CSS/DOM parser for .NET without relying on browsers or regex hacks.

Outcome

AngleSharp evolved from a solo prototype into a modular, community‑driven .NET library with hundreds of millions of downloads, enabling reliable HTML parsing and related tooling across the ecosystem.

Workflow

• 1. Identify need for a full HTML5 parser in .NET.
• 2. Start implementation on a flight using the HTML5 spec as reference.
• 3. Build core tokenizer, tree construction, and DOM APIs.
• 4. Iterate on edge cases and error handling to match browser behavior.
• 5. Publish initial code on GitHub and write a CodeProject article.
• 6. Engage community, accept contributions, and refactor for modularity (0.10 release).
• 7. Stabilize API, adopt semantic versioning, and release 1.0.
• 8. Expand ecosystem with satellite libraries (Css, Js, Xml, Io, Diffing, Wasm).
• 9. Maintain project under .NET Foundation and grow community.
• 10. Monitor adoption via NuGet downloads and community feedback.

Evidence

AngleSharp is a .NET library that parses HTML, SVG, MathML, CSS, and (to a good extent) XML, and gives you back a fully-featured, spec-conformant DOM.

Source

The repository already had 120+ stars, and the article was ranking surprisingly well.

Source

AngleSharp 0.10 laid the groundwork for modularity.

Source

Over 310 million downloads for the core package.

Source