SvelteKit performance tuning: push first paint and edge response to the limit
Around SvelteKit's real bottlenecks, an actionable LCP / INP / CLS checklist.
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Quick answer
Why does my SvelteKit site 404 on pure static hosting?
Forgetting prerender=true produces pages that require a server. Use adapter-static and explicitly enable prerender.
Machine-readable page data: /data/svelte-performance-optimization.json
In-depth analysis
Svelte compiles components to efficient imperative code at build time, leaving almost zero framework overhead at runtime. SvelteKit's adapter-static option produces pure SSG output, a natural fit for edge hosting. Performance tuning concentrates on three fronts — build-time code splitting, edge caching, and zero runtime dependencies — to push first paint and response time to their floor.
// svelte.config.js — static adapter (Cloudflare Pages)
import adapter from '@sveltejs/adapter-static';
export default {
kit: { adapter: adapter({ fallback: '200.html' }) }
};
// Pre-render: export const prerender = true;SvelteKit Performance Tuning · Key takeaways
- First-paint JS bundle audited
- Static assets hit edge long cache
- Core interaction INP measured ≤ 100ms
- Lighthouse hits the budget target
FAQ & pitfalls
How do I invalidate SvelteKit static build cache?
Atomic replacement of the build output: hash-named assets get immutable long cache, HTML gets must-revalidate. New content = new URL.
Explore the hub
See all 5 guides in SvelteKitSame category as this article, sorted across the codebase.
SvelteKit architecture: layered patterns for high-concurrency edge apps
The edge-delivery view of SvelteKit's layering and data flow.
SvelteKit best practices: engineering conventions for production
Field-tested SvelteKit practices from production, avoiding the common anti-patterns.
SvelteKit deployment guide: zero-ops edge publishing with Cloudflare Pages
Git-driven SvelteKit deployment in practice: commit to build, atomic publish to every edge node.
SvelteKit in practice: zero runtime overhead for static sites
Use Svelte compile-time optimization plus adapter-static to ship near-zero-JS static pages on the edge.
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What readers are asking
Questions that keep coming back in reader feedback, already answered.
- 01
Why is my Astro component's interactivity not working?
Components ship as zero-JS HTML by default, so an interactive one needs a client:* directive (client:load, client:visible, …). Without it the script is never bundled into the page.
See the full guide → - 02
Why is my custom Tailwind v4 brand colour not applied?
Colours must be declared in @theme (for example --color-brand). A missing @tailwindcss/vite plugin, or a leftover v3 config, makes bg-brand silently render nothing.
See the full guide → - 03
Why are _headers / _redirects not taking effect?
Both files must sit at the root of the output directory (dist/); anything under src/ is never uploaded. A purely static project should not add _worker.js either — that gives up the zero-cold-start advantage.
See the full guide →