Kobo can run apps now

Kobo, the popular e-reader, has gained the ability to run third-party apps starting today. This new feature is made possible by an open-source application platform called Cobalt. With Cobalt, Kobo e-readers now feature a launcher, an App Store, a Rust SDK, and a runtime that ensures each app operates in its own unprivileged process.

Once installed via USB, subsequent apps can be installed, updated, and removed directly on the device itself, over Wi-Fi. Rebooting the reader restores it to its original Kobo state. Every app is a static ARM binary that runs independently in its own unprivileged process, utilizing the device's hardware.

The App Store facilitates the installation, updates, and removals of apps over Wi-Fi, with signatures verified before any app launches. Photos of the upgraded device are presented, not simulator captures. The arXiv app, for instance, can now display HTML-rendered arXiv publications, complete with abstracts, sections, mathematical equations, and result tables, all paginated for optimal viewing on the panel.

All screenshots displayed are captures from a Kobo Clara BW. Store apps operate independently of the platform and always provide a route back to the Kobo reader. The installation, updates, removals, and reinstalls of signed apps over Wi-Fi are seamless. The Store also browses the newest preprints and reads their full text on the panel.

A unique feature allows users to send Morse code messages on the front light, with each letter spanning the entire panel. Research, writing, narrating, and playing an original audiobook are all possible. The platform also reads any OPDS library, including Project Gutenberg, Standard Ebooks, Open Library, or any custom library. It can discover a site's feed and present its articles without the site's layout, while collecting the day's stories in the background as you use another app.

Users can ask questions and receive touch-friendly responses. They can approve or deny requests from coding agents without needing to be at the keyboard. The UI toolkit provides controls, layouts, typography, and states for the panel. Connectivity, hardware, and platform updates are kept separate from the Store.

A persistent list with touch entry and completed-item states is available, along with two players that support partial refreshes for individual cells. The device's hall sensor, located behind the bezel, is reported and its changes are implemented. Apps do not have direct access to device resources; instead, they request them. Network, storage, audio, frontlight, and Wi-Fi capabilities are all gated, and a refusal is communicated as a value the app can handle.

App releases are completely independent of platform releases. A merge of an app pull request builds it for ARM, signs it, and updates the catalog, with no Cobalt version bump or reinstall needed. The Cobalt platform also updates over Wi-Fi through Settings, independently of the app catalog. The USB cable is only required once for installation and catalog transactions are recovery-safe.

The complete walkthrough, including recovery steps, is available in docs/INSTALL.md. App contributions are made through regular pull requests. If an app runs on your device and the PR shows it running, it will be merged and published. Cobalt is designed for the Kobo Clara BW model and requires hardware and firmware matching for installation.

Only the Clara BW profile has been hardware-tested. Installation modifies user storage files without warranty, and the platform is an independent project not affiliated with Rakuten Kobo.