Google unveils “Cahier” open-source app to showcase large-screen development

Google has released a new open-source Android sample app called Cahier, aimed at helping developers design productivity and creativity apps optimized for large-screen devices such as tablets and foldables. The project demonstrates best practices for multi-window support, adaptive layouts, and stylus-based inking.

Cahier — meaning “notebook” in French — functions as a note-taking app where users can combine text, drawings, and images in one workspace. It showcases the use of Android’s Ink API for low-latency handwriting, drag-and-drop operations, multi-instance windowing, and an offline-first architecture powered by Room database.

Key elements of the project include adaptive UI design using Material 3 components, desktop-style multitasking, and system integration through Android’s “notes role,” which allows an app to serve as the device’s default note-taking tool and respond to quick-access gestures or lock-screen prompts.

Google said the initiative aims to provide developers with an end-to-end example of building for larger screens, covering UI design, input methods, and performance optimization. Cahier is available as an open-source project for developers to explore, customize, and use as a foundation for building advanced productivity or creative Android apps.