uBlock Origin is a high-performance, wide-spectrum content blocker implemented as a browser extension for Chromium, Firefox, Edge, Opera, and Thunderbird. The architecture is a multi-platform browser extension with a core filtering engine (static network filtering, cosmetic filtering, scriptlet injection) written in highly optimized JavaScript with WebAssembly acceleration (custom HNTrie/BidiTrie compressed tries, LZ4 block codec, public suffix list). The MV2 variant uses webRequestBlocking for real-time request interception, while the MV3 variant (uBO Lite) uses declarativeNetRequest with offscreen documents for filter compilation. A standalone npm package (@gorhill/ubo-core) exposes the static network filtering engine for programmatic use outside the browser. The codebase demonstrates exceptional craftsmanship in its filtering engines: the static network filtering parser and matcher handle the full EasyList syntax plus extensive uBO-specific extensions (replace=, urlskip=, ipaddress=, header=, csp=, permissions=, etc.). The HNTrieContainer implements a compressed trie specialized for right-to-left hostname matching with both JS and WASM implementations. The cosmetic filtering engine supports procedural selectors, scriptlet injection with 50+ scriptlets, and HTML filtering. The s14e-serializer provides efficient binary serialization with LZ4 compression for fast engine state snapshots. Differential updates for filter lists minimize bandwidth. The code is meticulously optimized for CPU and memory efficiency, which is critical for a content blocker processing every network request.