snapchat/valdi

Valdi is a cross-platform UI framework created by Snapchat that lets you build mobile and desktop apps for iOS, Android, and macOS by writing code once in TypeScript. TypeScript is a version of JavaScript with added type safety, which helps catch mistakes early. What makes Valdi different from similar tools is that it compiles your code directly into native views, the real building blocks the operating system uses to draw the screen, rather than running a web browser inside your app or using a JavaScript bridge (a middle layer that translates between JavaScript and native code, which often causes performance slowdowns). The framework has been used inside Snap's own production apps for eight years before being open-sourced. You write your UI components in a style that looks like HTML-style tags inside TypeScript (called TSX), and Valdi compiles those to native elements on each platform. The layout engine is written in C++ and runs with minimal overhead. Performance features include automatic view recycling (reusing on-screen elements instead of recreating them) and viewport-aware rendering (only loading what is currently visible). For developers, Valdi offers instant hot reload (see code changes appear on-device in milliseconds without a full rebuild), full debugging support in VSCode and Cursor editors, and the ability to mix Valdi components into existing native app code gradually rather than rewriting everything at once. You can also write performance-critical code in C++, Swift, Kotlin, or Objective-C and connect it to your TypeScript layer with type-safe auto-generated bindings. Valdi is currently in beta and is free to use under the MIT license.