Our friends at Gatsby just announced the stable release of Gatsby themes. Chris Biscardi writes on the Gastby blog: Using a Gatsby theme, all of your default configuration (shared functionality, data sourcing, design) is abstracted out of your site, and into an installable package. This means that the configuration and functionality isn’t directly written into your project, but rather versioned, centrally managed, and installed as a dependency. You can seamlessly update a theme, compose themes together, and even swap out one compatible theme for another. What does “stable” mean? The core theme APIs have been stable for a long time under the __experimentalThemes flag in gatsby-config.js. Since they’re being used in production by a number of different companies to great effect, we’re promoting these APIs, specifically composition and shadowing, to stable within Gatsby core so that people can take advantage of them with confidence.