Capsule

Capsule is a format and a player for self-contained applications, from the project at withcapsule.app. An application built with it — the interface, the data and everything it needs — is packed into a single portable file with a .capsule extension, which someone else opens in a free host player on macOS, Windows or Linux, or previews in a browser. There is no cloud service behind it, no account to create and nothing to deploy: sharing the application means sending the file. Data lives inside the capsule in SQLite rather than in a hosted database, which is what makes the file self-sufficient and also what bounds it — this is a format for tools, internal utilities, prototypes and portfolio pieces that one person hands to another, not for a multi-user service. The host player and the format are free. The version available at the time of this listing was 0.5.2, so it is early and pre-1.0 by the project's own numbering, and that is the main caveat for anyone considering it for real work. It reached a wide audience through Hacker News on 16 September 2026 rather than through a product launch site. Not to be confused with the password manager or the CRM that share the name; this is the single-file application format.