A static site generator, or SSG, is a build-time tool that takes content and templates and produces a complete tree of plain HTML, CSS, and JavaScript files. Once generated, those files can be served from any web server or content delivery network without running application code or querying a database on each request. The model sits between hand-written static pages and fully dynamic server-rendered applications: the dynamism happens once, at build, rather than on every visit.
Jekyll, released by GitHub co-founder Tom Preston-Werner in 2008, popularized the modern form. Its documentation states plainly: “Jekyll is a static site generator. It takes text written in your favorite markup language and uses layouts to create a static website.” Authors write posts and pages in Markdown, define reusable layouts, and run a build that stitches them into a finished site. Jekyll became the engine behind GitHub Pages, which brought the workflow to a very large audience of developers.
The build-time approach gives several advantages. Because the output is just files, sites are fast to serve, cheap to host, resistant to many common attacks (there is no live database or server-side interpreter to exploit), and easy to cache at the edge. The content typically lives in version control alongside the templates, so a site’s history is tracked like source code.
Many generators followed, each with a different emphasis. Hugo, written in Go, focused on raw build speed for very large sites. Gatsby brought a React-based developer experience and a data layer. Eleventy aimed for simplicity and flexibility with minimal configuration. Astro combined static generation with a component model and selective hydration. Despite differences, all share the core idea of producing static output ahead of time.
Static site generators are a foundational piece of the Jamstack architecture, supplying the pre-rendered markup that gets pushed to a CDN. As frameworks matured, the strict boundary between “static generation” and “server-side rendering” blurred, with tools offering both per page, but the SSG remains the canonical way to pre-build a site into fast, durable, static files.