Nuxt 4 app patterns for hydration safety, performance, route rules, lazy loading, and SSR-safe data fetching with useFetch and useAsyncData. Use when building or reviewing a Nuxt 4 app, or debugging hydration mismatches and SSR-safe data fetching.

Nuxt 4 Patterns Use when building or debugging Nuxt 4 apps with SSR, hybrid rendering, route rules, or page level data fetching. When to Activate Hydration mismatches between server HTML and client state Route level rendering decisions such as prerender, SWR, ISR, or client only sections Performance work around lazy loading, lazy hydration, or payload size Page or component data fetching with useFetch , useAsyncData , or $fetch Nuxt routing issues tied to route params, middleware, or SSR/client differences Hydration Safety Keep the first render deterministic. Do not put Date.now() , Math.random() , browser only APIs, or storage reads directly into SSR rendered template state. Move browser only logic behind onMounted() , import.meta.client , ClientOnly , or a .client.vue component when the server cannot produce the same markup. Use Nuxt's useRoute() composable, not the one from vue router . Do not use route.fullPath to drive SSR rendered markup. URL fragments are client only, which can create hydration mismatches. Treat ssr: false as an escape hatch for truly browser only areas, not a default fix for mismatches. Data Fetching Prefer await useFetch() for SSR safe API reads in pages and components. It forwards server fetched data into the Nuxt payload and avoids a second fetch on hydration. Use useAsyncData() when the fetcher is not a simple $fetch() call, when you need a custom key, or when you are composing multiple async sources. Give useAsyncData() a stable key for cache reuse and predictable refresh behavior. Keep useAsyncData() handlers side effect free. They can run during SSR and hydration. Use $fetch() for user triggered writes or client only actions, not top level page data that should be hydrated from SSR. Use lazy: true , useLazyFetch() , or useLazyAsyncData() for non critical data that should not block navigation. Handle status === 'pending' in the UI. Use server: false only for data that is not needed for SEO or the first paint. Trim payload size with pick and prefer shallower payloads when deep reactivity is unnecessary. Route Rules Prefer routeRules in nuxt.config.ts for rendering and caching strategy: prerender : static HTML at build time swr : serve cached content and revalidate in the background isr : incremental static regeneration on supported platforms ssr: false : client rendered route cache or redirect : Nitro level response behavior Pick route rules per route group, not globally. Marketing pages, catalogs, dashboards, and APIs usually need different strategies. Lazy Loading and Performance Nuxt already code splits pages by route. Keep route boundaries meaningful before micro optimizing component splits. Use the Lazy prefix to dynamically import non critical components. Conditionally render lazy components with v if so the chunk is not loaded until the UI actually needs it. Use lazy hydration for below the fold or non critical interactive UI. For custom strategies, use defineLazyHydrationComponent() with a visibility or idle strategy. Nuxt lazy hydration works on single file components. Passing new props to a lazily hydrated component will trigger hydration immediately. Use NuxtLink for internal navigation so Nuxt can prefetch route components and generated payloads. Review Checklist First SSR render and hydrated client render produce the same markup Page data uses useFetch or useAsyncData , not top level $fetch Non critical data is lazy and has explicit loading UI Route rules match the page's SEO and freshness requirements Heavy interactive islands are lazy loaded or lazily hydrated

nuxt4-patterns