Svelte vs SolidJS: A Technical Comparison

An in-depth analysis of two reactive frameworks challenging React's dominance.

This post was originally published on Medium.

Overview

Both Svelte and SolidJS take fundamentally different approaches to reactivity compared to React — and to each other. Understanding those differences is the key to choosing the right tool for your production application.

Compilation Strategies

Svelte compiles away at build time. There is no runtime virtual DOM — the compiler converts your components into highly optimized imperative JavaScript. The result is tiny bundle sizes and predictable performance characteristics.

SolidJS takes a different approach. It compiles JSX to fine-grained reactive operations, but unlike Svelte, it does ship a small runtime. The trade-off is a React-like authoring experience with Svelte-level performance.

Reactivity Models

Svelte uses a declaration-based reactivity model. You declare reactive variables with $: prefixes, and the compiler tracks dependencies at build time.

let count = 0;
$: doubled = count * 2;

SolidJS uses signals — primitives similar to observables that automatically track subscriptions at runtime. This fine-grained tracking means only the exact DOM nodes that depend on a signal update, not entire components.

const [count, setCount] = createSignal(0);
const doubled = () => count() * 2;

Performance Trade-offs

In benchmarks, both significantly outperform React in raw update throughput. SolidJS consistently ranks near the top of the js-framework-benchmark suite. Svelte performs excellently at initial load due to zero runtime overhead.

For most production applications, the difference is imperceptible. The real deciding factor is ecosystem maturity and team familiarity.

When to Choose Which

Choose Svelte when bundle size is a hard constraint, your team prefers a gentler learning curve, and you're building content-focused or marketing sites.

Choose SolidJS when your team is already comfortable with React patterns, you need the finest-grained reactivity possible, and you're building highly interactive, data-dense applications.

Both are excellent choices. The "React dominance" narrative is changing — these frameworks prove that compiled reactivity is the future.