Fix MemoryError in Svelte When Deploying

SvelteKit Build Memory Errors

SvelteKit uses Vite under the hood, and building large projects can exhaust Node.js memory. Here's how to fix it.

Increase Node.js Heap

{
  "scripts": {
    "build": "node --max-old-space-size=4096 node_modules/.bin/vite build"
  }
}

Or with SvelteKit's CLI:

NODE_OPTIONS="--max-old-space-size=4096" npm run build

Large Route Count

SvelteKit prerenders routes at build time. Thousands of routes consume proportional memory:

// svelte.config.js
export default {
  kit: {
    prerender: {
      entries: ['*'],
      concurrency: 2, // Reduce concurrent prerender jobs
    }
  }
};

Or disable prerendering for dynamic routes and use SSR instead:

// src/routes/products/[id]/+page.ts
export const prerender = false;

Dependency Optimization

Vite's dependency pre-bundling can consume lots of memory with many packages:

// vite.config.ts
export default defineConfig({
  optimizeDeps: {
    exclude: ['heavy-package-not-needed-in-dev'],
  },
  build: {
    rollupOptions: {
      output: {
        manualChunks: {
          vendor: ['lodash', 'date-fns'],
        }
      }
    }
  }
});

Docker Builds

FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
ENV NODE_OPTIONS="--max-old-space-size=4096"
RUN npm run build

Ensure your Docker builder has at least 4GB RAM allocated.

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