Vite

Vite Configuration Patterns

Basic Setup

// vite.config.ts
import { defineConfig } from "vite";
import react from "@vitejs/plugin-react";

export default defineConfig({
    plugins: [react()],
});

Use defineConfig for type safety and IntelliSense.

Conditional Configuration

export default defineConfig(({ command, mode }) => {
    const isDev = command === "serve";
    const isProd = mode === "production";

    return {
        plugins: [react()],
        build: {
            sourcemap: isDev,
            minify: isProd ? "esbuild" : false,
        },
    };
});

• command is "serve" (dev) or "build" (production).
• mode is "development", "production", or custom.

Path Aliases

import { resolve } from "path";

export default defineConfig({
    resolve: {
        alias: {
            "@": resolve(__dirname, "src"),
            "@components": resolve(__dirname, "src/components"),
            "@lib": resolve(__dirname, "src/lib"),
        },
    },
});

Match aliases in tsconfig.json:

{
    "compilerOptions": {
        "paths": {
            "@/*": ["./src/*"],
            "@components/*": ["./src/components/*"],
            "@lib/*": ["./src/lib/*"],
        },
    },
}

Environment Variables

Variables must be prefixed with VITE_ to be exposed to client code:

# .env
VITE_API_URL=https://api.example.com
VITE_APP_TITLE=My App

# Not exposed to client (server-only)
DATABASE_URL=postgres://...
API_SECRET=secret

// Access in code
const apiUrl = import.meta.env.VITE_API_URL;
const mode = import.meta.env.MODE; // "development" | "production"
const isDev = import.meta.env.DEV; // boolean
const isProd = import.meta.env.PROD; // boolean

Type-Safe Env

// src/vite-env.d.ts
/// <reference types="vite/client" />

interface ImportMetaEnv {
    readonly VITE_API_URL: string;
    readonly VITE_APP_TITLE: string;
}

interface ImportMeta {
    readonly env: ImportMetaEnv;
}

Env File Priority

.env                # loaded in all cases
.env.local          # loaded in all cases, gitignored
.env.[mode]         # loaded for specific mode
.env.[mode].local   # loaded for specific mode, gitignored

Dev Server Proxy

Proxy API requests to a backend server:

export default defineConfig({
    server: {
        port: 3000,
        proxy: {
            "/api": {
                target: "http://localhost:8080",
                changeOrigin: true,
            },
            "/api/v2": {
                target: "http://localhost:8081",
                rewrite: (path) => path.replace(/^\/api\/v2/, ""),
            },
            "/ws": {
                target: "ws://localhost:8080",
                ws: true,
            },
        },
    },
});

Plugins

Plugin Order

export default defineConfig({
    plugins: [
        pluginA(), // default order
        pluginB({ enforce: "pre" }), // runs before Vite core
        pluginC({ enforce: "post" }), // runs after Vite build
    ],
});

Conditional Plugins

export default defineConfig(({ command }) => ({
    plugins: [
        react(),
        command === "build" && visualizer(), // only during build
        command === "serve" && inspector(), // only during dev
    ].filter(Boolean),
}));

Common Plugins

Build Optimization

Code Splitting

Vite splits code automatically at dynamic imports. Customize chunking:

export default defineConfig({
    build: {
        rollupOptions: {
            output: {
                manualChunks: {
                    vendor: ["react", "react-dom"],
                    router: ["react-router"],
                    query: ["@tanstack/react-query"],
                },
            },
        },
    },
});

Dynamic Manual Chunks

manualChunks(id) {
  if (id.includes("node_modules")) {
    if (id.includes("react")) return "vendor";
    if (id.includes("@tanstack")) return "tanstack";
    return "deps";
  }
},

Build Targets

export default defineConfig({
    build: {
        target: "es2022", // modern browsers
        minify: "esbuild", // fast (default), or "terser" for smaller output
        cssMinify: "lightningcss", // faster CSS minification
        sourcemap: true, // enable for production debugging
        reportCompressedSize: false, // skip gzip size reporting (faster builds)
    },
});

Chunk Size Warnings

build: {
  chunkSizeWarningLimit: 500, // KB, default is 500
},

Library Mode

Build a library for npm distribution:

export default defineConfig({
    build: {
        lib: {
            entry: resolve(__dirname, "src/index.ts"),
            name: "MyLib",
            formats: ["es", "cjs"],
            fileName: (format) => `my-lib.${format}.js`,
        },
        rollupOptions: {
            external: ["react", "react-dom"],
            output: {
                globals: {
                    react: "React",
                    "react-dom": "ReactDOM",
                },
            },
        },
    },
});

For library bundling, consider tsdown instead — it handles DTS generation, multiple entries, and package.json exports more elegantly.

CSS

CSS Modules

// Automatically enabled for *.module.css files
import styles from "./button.module.css";

// Configure behavior
export default defineConfig({
    css: {
        modules: {
            localsConvention: "camelCaseOnly",
            generateScopedName: "[name]__[local]___[hash:base64:5]",
        },
    },
});

PostCSS

export default defineConfig({
    css: {
        postcss: "./postcss.config.js",
    },
});

Lightning CSS

export default defineConfig({
    css: {
        transformer: "lightningcss",
        lightningcss: {
            targets: browserslistToTargets(browserslist(">= 0.25%")),
        },
    },
});

Static Assets

// Import as URL
import logo from "./logo.svg";

// Import as string
import shaderCode from "./shader.glsl?raw";

// Import as worker
import Worker from "./worker.js?worker";

Public Directory

Files in public/ are served at root and copied as-is to build output. Use for favicons, robots.txt, and files that must keep their exact filename.

Preview

Preview production builds locally:

vite preview --port 4173

export default defineConfig({
    preview: {
        port: 4173,
        strictPort: true,
    },
});

Performance Tips

• Dependency pre-bundling: Vite pre-bundles node_modules with esbuild. Use optimizeDeps.include to pre-bundle deps that are dynamically imported.
• Avoid barrel re-exports: Barrel files (index.ts exporting everything) defeat tree-shaking in dev. Import directly when possible.
• Use reportCompressedSize: false: Disables gzip size computation for faster builds.
• Split vendor chunks: Separate stable vendor code from frequently changing app code.