What is SSR vs CSR & Hydration?
Server rendering delivers complete HTML fast; client rendering builds it in the browser; hydration animates the server HTML into an interactive app. Content pages render on the server by default.
Related terms
Server-Side Rendering
Rendering full HTML on the server per request so crawlers and users receive complete content immediately. The SEO-safe default for content pages in frameworks like SvelteKit and Next.js.
Client-Side Rendering
Building page content in the browser with JavaScript after an initially thin HTML shell. Flexible for apps, but critical content and links should still be server-available for crawlers and fast paint.
JavaScript SEO
Making client-rendered pages discoverable: crawlable links, server or prerendered critical content, unblocked resources, and unique URLs per state. Rendering usually happens, but slow tails hurt time-sensitive pages.
Svelte Runes
The `$state`, `$derived`, `$effect`, and `$props` primitives powering Svelte 5 reactivity. Runes are mandatory in generated code: explicit, compilable, and consistent across every component.
File-Based Routing
Pages defined by file location: `+page.svelte` renders, `+layout.svelte` wraps, `+server.js` serves data. The route tree is the app map — no separate router config to drift.
Load Function
Server-side data loading for a route before it renders. Load on the server for content crawlers and users need immediately; reach for client fetching only for interactive extras.