React vs. Solid vs. Svelte: Real-World Performance Comparison

React, Solid, and Svelte all ship modern DX and production-ready ecosystems—but they make very different trade-offs under the hood. If you’re building an interactive site or app and care about how fast things feel in users’ hands, the differences matter.

This article summarizes what typically wins where, how to reproduce realistic measurements on your own hardware, and how Astro’s island architecture can help you ship less client JavaScript no matter which UI library you prefer.

TL;DR

• Startup and initial load: Svelte often ships the smallest runtime and fast startup; Solid is close, especially with fine-grained hydration; React can be larger by default, but React Server Components (RSC) and code-splitting narrow the gap.
• Hydration cost: Solid’s fine-grained approach generally hydrates less and updates faster; Svelte’s compiled output is efficient; React’s hydration can be heavier unless you limit client components and use selective hydration patterns.
• Runtime updates and interactivity: Solid frequently leads in per-update latency due to signal-based reactivity; Svelte is typically very fast with minimal bookkeeping; React is competitive when state is well-partitioned and memoization is thoughtfully applied.
• Ecosystem and scalability: React still wins on ecosystem breadth and third-party integrations. Solid and Svelte ecosystems are mature enough for production but smaller.
• Biggest lever: Architecture beats micro-optimization. Use SSR, split code, and send less JS. Astro islands plus partial/controlled hydration can erase most differences for content-heavy sites.

What we measured

• Initial render time: SSR TTFB and largest contentful paint (LCP) after hydration.
• Hydration overhead: Time spent attaching event listeners and making the page interactive.
• Interactivity latency: Time to respond to user input (typing, clicking, filtering).
• Update throughput: Re-rendering lists (1k–5k rows), toggling items, and frequent state updates.
• Bundle and runtime cost: Client JS size after code-splitting and gzipping, plus main-thread JS execution time.
• Memory behavior: Rough footprint under sustained interaction.

How the frameworks differ

• React: Virtual DOM with reconciliation. Strong ecosystem, RSC reduces client JS when used well. By default, more runtime and hydration work, but highly tunable.
• Solid: Fine-grained reactivity via signals. Minimal overhead on updates and during hydration. Small runtime, strong performance under dynamic workloads.
• Svelte: Compile-time reactivity. No virtual DOM; generates targeted DOM operations. Small bundles and quick startup; great default ergonomics and speed.

Real-world test scenarios

1. Content-first route with small interactive widgets

• SSR page with hero, article text, and 2–3 interactive islands (accordion, search box).
• Measure: TTFB, LCP, hydration time of islands, JS executed on load.

2. Data list with frequent updates

• 1k-row table with add/remove, filter, and “toggle all” interactions.
• Measure: Input-to-paint latency, total update time, dropped frames.

3. Controlled form with validation

• 20–50 inputs, live validation, dependent fields.
• Measure: Keystroke latency, CPU time per change, memory stability.

4. Navigation between similar pages

• Client transitions with preserved layout and changing data.
• Measure: Transition time, network + CPU breakdown, cache effectiveness.

How to reproduce fair tests locally Hardware

• Desktop: modern CPU laptop/desktop.
• Mobile: mid-range Android (e.g., 2–3 years old).
• Throttle: 4x CPU downclock and 3G Fast network in Chrome DevTools for repeatability.

Tools

• Chrome DevTools Performance panel for CPU/JS breakdowns.
• Lighthouse (lab), WebPageTest (field-like), and/or Safari/WebKit for cross-engine sanity checks.
• Framework devtools where applicable (React Profiler, Solid Devtools, Svelte Devtools).

Build-and-measure checklist

• Build production bundles: ensure minification, tree-shaking, and code-splitting.
• SSR when possible: measure both SSR+hydrate and client-only SPA.
• Disable dev-only flags and source maps in timing runs.
• Record multiple runs; report medians.

Starter setups (Vite)

• React (SWC):
  • npm create vite@latest react-perf — —template react-swc
  • cd react-perf && npm i && npm run build && npm run preview
• Solid:
  • npm create vite@latest solid-perf — —template solid
  • cd solid-perf && npm i && npm run build && npm run preview
• Svelte:
  • npm create vite@latest svelte-perf — —template svelte
  • cd svelte-perf && npm i && npm run build && npm run preview

Add the same test widget to each project (example: 1k-row list with toggle, filter, and add/remove) and measure with the Performance panel. Keep identical data sizes and interaction patterns.

Typical results you’ll see

• Startup and bundle size:

  • Svelte tends to lead with the smallest client JS for comparable features, yielding quick startup.
  • Solid is also lean and competitive, particularly when you avoid heavy wrappers and keep signals local.
  • React’s baseline bundle can be larger, but RSC, selective client components, and route-level code-splitting substantially reduce shipped JS.

• Hydration and interactivity:

  • Solid’s fine-grained hydration generally reduces work, making input latency hard to beat in dynamic widgets.
  • Svelte’s compiled DOM ops keep hydration and updates crisp with minimal bookkeeping.
  • React performs well with memoization, useMemo/useCallback, keyed lists, and splitting state to avoid broad rerenders. Without care, hydration and update work can increase.

• Large lists and frequent updates:

  • Solid typically leads thanks to signal granularity and minimal diffing.
  • Svelte is close, especially when each item’s state is localized and updates are targeted.
  • React can be competitive with windowing (react-window), key stability, and memoization to constrain reconciliation.

• Complex forms:

  • All three can be excellent when validation is localized and expensive work is debounced.
  • Solid generally shows lower per-keystroke overhead; Svelte is similarly crisp; React benefits heavily from controlled vs. uncontrolled choices and stable handlers.

What can swamp framework differences

• Over-fetching data or large JSON payloads.
• Unchunked hydration and long-running effects on mount.
• Unbounded list rendering without windowing.
• Client-side routing that eagerly loads heavy routes.
• Global state updates that cascade through many components.

Best practices to make any of them fast

• Ship less JS:
  • SSR by default. Use code-splitting and lazy routes/components.
  • Prefer server-side data fetching and stream HTML where supported.
  • Defer non-critical interactivity.
• Contain updates:
  • Localize state and avoid global cascades.
  • In React, memoize carefully and keep props stable.
  • In Solid/Svelte, prefer fine-grained reactive stores/signals.
• Render less:
  • Virtualize long lists.
  • Split components so small parts update without touching siblings.
• Hydrate smarter:
  • Delay non-critical islands until idle or visible.
  • Prefer partial/controlled hydration where your stack supports it.

Where Astro fits

• Astro renders HTML by default and hydrates only the components you mark as interactive. This cuts client JavaScript regardless of whether you use React, Solid, or Svelte.
• For content-heavy sites (docs, blogs, marketing), Astro’s islands often erase startup and hydration differences between frameworks entirely because you ship very little JS to begin with.
• For app-like pages, Astro still helps by scoping interactivity to islands and deferring hydration until needed.

When to pick which

• Choose Solid if:
  • You need top-tier interactivity performance, fine-grained updates, and low hydration overhead.
  • You like signals and a small runtime.
• Choose Svelte if:
  • You want small bundles and great defaults via a compiler-driven model.
  • You prefer declarative, minimal boilerplate and fast startup.
• Choose React if:
  • You rely on its ecosystem, RSC, and broad library support.
  • You can invest in architectural optimizations (RSC, code-splitting, memoization) to reach competitive performance.

A minimal, comparable widget example

• Behavior: render 1,000 items, toggle items, filter by text, and add/remove.
• Tips:
  • Keep item shape identical across frameworks.
  • Use keyed lists.
  • Batch updates where supported (React 18 does automatically in many cases).
  • Measure input latency while filtering and toggling all items.

Validation rubric for your results

• Use the same data set and UI across frameworks.
• Use production builds with identical image/fonts strategies.
• Measure on both desktop and a mid-range phone with throttling.
• Report median of multiple runs and attach profiles for traceability.

Final thoughts

• All three are capable of excellent performance. Differences in default behavior and runtime models show up most in hydration and frequent updates.
• Architecture dominates micro-benchmarks. SSR, code-splitting, and Astro-style islands will do more for real users than switching frameworks alone.
• If you already have a preferred ecosystem, apply the practices above. If you’re starting fresh and care about dynamic UI speed, Solid and Svelte are strong defaults; for ecosystem breadth and RSC-driven architectures, React remains a safe bet.