These pages cover the building blocks of a Fresh application. Read them in order for a guided tour, or jump to what you need. ## Routing & data - [**Routing**](/docs/concepts/routing) — turn files in `routes/` into URLs, with dynamic params, catch-alls, and route groups. - [**Routes**](/docs/concepts/routes) — what a route file looks like: handler + page, return values, GET vs POST. - [**Context**](/docs/concepts/context) — the `ctx` object every handler and middleware receives. - [**Middleware**](/docs/concepts/middleware) — run logic before routes: auth, logging, shared state. ## Rendering - [**Layouts**](/docs/concepts/layouts) — wrap groups of routes in shared UI. - [**App shell**](/docs/concepts/app-shell) — the `` document around every page. - [**Error pages**](/docs/concepts/error-pages) — render 404s, 500s, and thrown errors. ## Interactivity - [**Islands**](/docs/concepts/islands) — components hydrated in the browser. - [**Signals & reactivity**](/docs/concepts/signals) — reactive state, on the page and inside islands. - [**Event handlers**](/docs/concepts/events) — wire up `onClick`/`onInput` without an island.