Lynx: ByteDance’s UI Framework Goes Open Source

Lynx, a cross-platform UI framework developed by ByteDance, was made open-source by its development team on March 5. The framework aims to help web developers leverage their existing skills to build native interfaces for both mobile and web platforms simultaneously. Already deployed in applications like TikTok, the framework boasts high-performance capabilities, a multi-functional rendering engine, and a modern Rust-based toolchain.

The framework embraces familiar web development paradigms, supporting CSS animations, selectors, and variables to ensure flexible and modern interface customization. Its most distinctive architectural decision involves splitting user scripts across two independent runtimes:

A main thread runtime driven by the PrimJS engine, handling high-priority events

A background runtime ensuring low-load and non-blocking main thread operations

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Lynx has two performance highlights:

Instant First-Frame Rendering (IFR): By briefly blocking the main thread, Lynx ensures the first frame is completely rendered, providing an immediate response user experience.

Main Thread Script (MTS): A static-scheduled code segment handling high-priority events and gestures, enabling native-like interaction feel.

Originally developed by ByteDance’s engineering team, Lynx has received significant support from TikTok. The platform has backed the framework’s open-source release, providing financial, technical, and community support.

The framework is particularly suited for diverse, rich-interaction scenarios, offering web developers a powerful tool to create cross-platform interfaces with a single codebase.

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