Capsule

Capsule is a format and player for self-contained applications, built around a single portable file. An application built with it, including its interface and data, is packed into one file with a .capsule extension. Someone else opens that file in a host player or previews it in a browser, and there is no server, account or cloud service behind it.

Features

• Single file: the interface, assets and local data of an application sit in one .capsule file that can be sent like a document.
• Embedded database: data is stored inside the file in SQLite rather than in a hosted database.
• Host player: opens capsules on macOS, Windows or Linux, and capsules can also be previewed in a browser.
• Standard web code: built from standard HTML, CSS and JavaScript, or started from a plain description.
• Local running: the tools run on the machine without an internet connection.

Customers and markets

One person handing a tool, prototype or portfolio piece to another. The format is not meant for a multi-user service.

Key facts

• Version: 0.5.2, so the format is pre-1.0 by the project's own numbering.
• Reach: word spread through Hacker News on 16 September 2026, not through a launch site.