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performance-optimization

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更新日2026年1月29日 18:59

Optimize Next.js portfolio for Core Web Vitals, bundle size, loading performance, and achieve 90+ Lighthouse scores.

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JaivishChauhan

JaivishChauhan/vibecoding-starter

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Performance Optimization Mastery

Core Philosophy

Performance is not an afterthought—it's a feature. A slow portfolio loses visitors and creates a poor first impression. We optimize for Core Web Vitals because Google uses them for ranking, but more importantly, because users deserve fast experiences.

Core Web Vitals Targets

Metric	Target	Description
LCP (Largest Contentful Paint)	< 2.5s	How fast the main content loads
FID (First Input Delay) / INP	< 100ms	How responsive to user input
CLS (Cumulative Layout Shift)	< 0.1	Visual stability (no jumping content)
FCP (First Contentful Paint)	< 1.8s	First visible content
TTFB (Time to First Byte)	< 600ms	Server response time

Image Optimization

Next.js Image Component (Essential)

import Image from 'next/image';

// ✅ Local images (automatic optimization)
import heroImage from '@/public/images/hero.jpg';

<Image
  src={heroImage}
  alt="Hero section"
  placeholder="blur"          // Blur-up loading effect
  priority                    // Load immediately (above-the-fold)
  className="object-cover"
  sizes="100vw"              // Responsive sizing hints
/>

// ✅ Remote images
<Image
  src="https://example.com/image.jpg"
  alt="Project screenshot"
  width={1200}
  height={630}
  loading="lazy"             // Default behavior
  quality={85}               // Compression (default: 75)
  className="object-cover"
  sizes="(max-width: 768px) 100vw, (max-width: 1200px) 50vw, 33vw"
/>

Image Configuration

// next.config.js
/** @type {import('next').NextConfig} */
const nextConfig = {
  images: {
    // Modern formats
    formats: ["image/avif", "image/webp"],

    // Remote patterns
    remotePatterns: [
      {
        protocol: "https",
        hostname: "images.unsplash.com",
      },
      {
        protocol: "https",
        hostname: "cdn.sanity.io",
      },
    ],

    // Device breakpoints
    deviceSizes: [640, 750, 828, 1080, 1200, 1920, 2048],
    imageSizes: [16, 32, 48, 64, 96, 128, 256, 384],

    // Minimize processing (if using external CDN)
    // unoptimized: true,
  },
};

module.exports = nextConfig;

Image Best Practices

// 1. Always use sizes prop for responsive images
<Image
  src="/project.jpg"
  alt="Project"
  fill
  sizes="(max-width: 768px) 100vw, (max-width: 1200px) 50vw, 33vw"
/>

// 2. Use priority for above-the-fold images (hero, profile)
<Image src={heroImage} alt="Hero" priority />

// 3. Lazy load below-the-fold images (default)
<Image src={projectImage} alt="Project" loading="lazy" />

// 4. Prevent CLS with aspect ratio containers
<div className="relative aspect-video">
  <Image src="/video-thumb.jpg" alt="Video" fill className="object-cover" />
</div>

Font Optimization

Next.js Font System

// app/layout.tsx
import { Inter, Playfair_Display } from "next/font/google";
import localFont from "next/font/local";

// Google Fonts (self-hosted, optimized)
const inter = Inter({
  subsets: ["latin"],
  display: "swap", // Prevent FOIT (flash of invisible text)
  variable: "--font-inter",
  preload: true,
});

const playfair = Playfair_Display({
  subsets: ["latin"],
  display: "swap",
  variable: "--font-playfair",
  weight: ["400", "700"], // Only load needed weights
});

// Local fonts (maximum control)
const calSans = localFont({
  src: "../public/fonts/CalSans-SemiBold.woff2",
  variable: "--font-cal",
  display: "swap",
  preload: true,
});

export default function RootLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <html
      lang="en"
      className={`${inter.variable} ${playfair.variable} ${calSans.variable}`}
    >
      <body className="font-sans">{children}</body>
    </html>
  );
}

Font Subsetting

// Only load characters you need
const inter = Inter({
  subsets: ["latin"], // Not 'latin-ext' unless needed
  display: "swap",
});

// For icons/special characters, use local subset
const customFont = localFont({
  src: "../fonts/custom-subset.woff2", // Pre-subsetted
});

Bundle Optimization

Package Import Optimization

// next.config.js
/** @type {import('next').NextConfig} */
const nextConfig = {
  experimental: {
    // Tree-shake package imports automatically
    optimizePackageImports: [
      "lucide-react",
      "framer-motion",
      "@radix-ui/react-icons",
      "date-fns",
      "lodash",
    ],
  },
};

Dynamic Imports (Code Splitting)

import dynamic from "next/dynamic";

// Heavy components loaded on demand
const HeavyChart = dynamic(() => import("@/components/heavy-chart"), {
  loading: () => <Skeleton className="h-96" />,
  ssr: false, // Client-only component
});

// Modal loaded when needed
const ContactModal = dynamic(() => import("@/components/contact-modal"));

// Animation components (reduce initial bundle)
const MotionDiv = dynamic(
  () => import("framer-motion").then((mod) => mod.motion.div),
  { ssr: false },
);

Analyze Bundle Size

// package.json
{
  "scripts": {
    "analyze": "ANALYZE=true next build"
  },
  "devDependencies": {
    "@next/bundle-analyzer": "^14.0.0"
  }
}

// next.config.js
const withBundleAnalyzer = require("@next/bundle-analyzer")({
  enabled: process.env.ANALYZE === "true",
});

module.exports = withBundleAnalyzer(nextConfig);

Import Optimization Patterns

// ❌ Bad: Imports entire library
import _ from "lodash";
_.debounce(fn, 300);

// ✅ Good: Tree-shakeable import
import debounce from "lodash/debounce";
debounce(fn, 300);

// ❌ Bad: All icons imported
import * as Icons from "lucide-react";

// ✅ Good: Only what you need
import { ArrowRight, Github, Mail } from "lucide-react";

// ❌ Bad: Moment.js (huge library)
import moment from "moment";

// ✅ Good: date-fns (tree-shakeable)
import { format, formatDistance } from "date-fns";

Rendering Strategies

Static Generation (Fastest)

// app/projects/page.tsx
// Statically generated at build time

export default async function ProjectsPage() {
  const projects = await getProjects(); // Fetched at build time

  return (
    <div>
      {projects.map((p) => (
        <ProjectCard key={p.id} project={p} />
      ))}
    </div>
  );
}

// Generate static paths
export async function generateStaticParams() {
  const projects = await getProjects();
  return projects.map((p) => ({ slug: p.slug }));
}

Incremental Static Regeneration (ISR)

// app/blog/page.tsx
// Revalidate every hour

export const revalidate = 3600; // seconds

export default async function BlogPage() {
  const posts = await getPosts();
  return <BlogList posts={posts} />;
}

// Per-fetch revalidation
async function getPosts() {
  const res = await fetch("https://api.example.com/posts", {
    next: { revalidate: 3600 },
  });
  return res.json();
}

On-Demand Revalidation

// app/api/revalidate/route.ts
import { revalidatePath, revalidateTag } from "next/cache";
import { NextRequest, NextResponse } from "next/server";

export async function POST(request: NextRequest) {
  const { secret, path, tag } = await request.json();

  if (secret !== process.env.REVALIDATION_SECRET) {
    return NextResponse.json({ error: "Invalid secret" }, { status: 401 });
  }

  if (path) {
    revalidatePath(path);
  }

  if (tag) {
    revalidateTag(tag);
  }

  return NextResponse.json({ revalidated: true });
}

Loading Performance

Streaming with Suspense

// app/page.tsx
import { Suspense } from "react";
import { HeroSection } from "@/components/sections/hero";
import { ProjectsSkeleton } from "@/components/skeletons";

// Projects component fetches its own data
async function ProjectsSection() {
  const projects = await getProjects(); // This can be slow
  return <ProjectsList projects={projects} />;
}

export default function HomePage() {
  return (
    <main>
      {/* Hero loads immediately */}
      <HeroSection />

      {/* Projects stream in when ready */}
      <Suspense fallback={<ProjectsSkeleton />}>
        <ProjectsSection />
      </Suspense>
    </main>
  );
}

Loading States

// app/projects/loading.tsx
import { Skeleton } from "@/components/ui/skeleton";

export default function ProjectsLoading() {
  return (
    <div className="container py-12">
      {/* Header skeleton */}
      <div className="mx-auto max-w-2xl text-center">
        <Skeleton className="mx-auto h-4 w-24" />
        <Skeleton className="mx-auto mt-2 h-10 w-80" />
        <Skeleton className="mx-auto mt-4 h-6 w-96" />
      </div>

      {/* Grid skeleton */}
      <div className="mt-16 grid gap-8 md:grid-cols-2 lg:grid-cols-3">
        {Array.from({ length: 6 }).map((_, i) => (
          <div key={i} className="rounded-2xl border border-zinc-800 p-6">
            <Skeleton className="aspect-video rounded-lg" />
            <Skeleton className="mt-4 h-6 w-3/4" />
            <Skeleton className="mt-2 h-4 w-full" />
            <Skeleton className="mt-2 h-4 w-2/3" />
          </div>
        ))}
      </div>
    </div>
  );
}

Skeleton Component

// components/ui/skeleton.tsx
import { cn } from "@/lib/utils";

interface SkeletonProps extends React.HTMLAttributes<HTMLDivElement> {}

export function Skeleton({ className, ...props }: SkeletonProps) {
  return (
    <div
      className={cn("animate-pulse rounded-md bg-zinc-800", className)}
      {...props}
    />
  );
}

Preloading & Prefetching

Link Prefetching

import Link from 'next/link';

// Automatic prefetch on viewport enter (production)
<Link href="/projects">Projects</Link>

// Disable prefetch for less important links
<Link href="/privacy" prefetch={false}>Privacy Policy</Link>

Resource Hints

// app/layout.tsx
export default function RootLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <html lang="en">
      <head>
        {/* Preconnect to external origins */}
        <link rel="preconnect" href="https://fonts.googleapis.com" />
        <link
          rel="preconnect"
          href="https://fonts.gstatic.com"
          crossOrigin="anonymous"
        />

        {/* DNS prefetch for analytics */}
        <link rel="dns-prefetch" href="https://www.googletagmanager.com" />

        {/* Preload critical assets */}
        <link
          rel="preload"
          href="/fonts/CalSans-SemiBold.woff2"
          as="font"
          type="font/woff2"
          crossOrigin="anonymous"
        />
      </head>
      <body>{children}</body>
    </html>
  );
}

Animation Performance

GPU-Accelerated Properties

// ✅ Good: GPU-accelerated (transform, opacity)
<motion.div
  initial={{ opacity: 0, y: 20 }}
  animate={{ opacity: 1, y: 0 }}
/>

// ❌ Bad: Triggers layout (width, height, left, top)
<motion.div
  initial={{ width: 0 }}
  animate={{ width: 200 }}
/>

Reduce Motion for Accessibility

"use client";

import { useReducedMotion } from "framer-motion";

export function AnimatedComponent() {
  const shouldReduceMotion = useReducedMotion();

  return (
    <motion.div
      initial={shouldReduceMotion ? false : { opacity: 0, y: 20 }}
      animate={{ opacity: 1, y: 0 }}
      transition={shouldReduceMotion ? { duration: 0 } : { duration: 0.5 }}
    >
      Content
    </motion.div>
  );
}

CSS-Based Animations (Lower Overhead)

// For simple animations, CSS is lighter than Framer Motion

// tailwind.config.ts
animation: {
  'fade-in': 'fade-in 0.5s ease-out forwards',
  'slide-up': 'slide-up 0.5s ease-out forwards',
},
keyframes: {
  'fade-in': {
    from: { opacity: '0' },
    to: { opacity: '1' },
  },
  'slide-up': {
    from: { opacity: '0', transform: 'translateY(20px)' },
    to: { opacity: '1', transform: 'translateY(0)' },
  },
},

// Usage
<div className="animate-fade-in">Content</div>

Caching Strategies

Fetch Caching

// Cache indefinitely (static data)
const data = await fetch("https://api.example.com/static", {
  cache: "force-cache",
});

// No caching (always fresh)
const data = await fetch("https://api.example.com/realtime", {
  cache: "no-store",
});

// Revalidate after time
const data = await fetch("https://api.example.com/posts", {
  next: { revalidate: 3600 },
});

// Tag-based revalidation
const data = await fetch("https://api.example.com/posts", {
  next: { tags: ["posts"] },
});

React Cache

import { cache } from "react";

// Deduplicate calls within same request
export const getUser = cache(async (id: string) => {
  const res = await fetch(`/api/users/${id}`);
  return res.json();
});

// Both components call getUser - only ONE fetch happens
async function UserHeader({ userId }: { userId: string }) {
  const user = await getUser(userId);
  return <h1>{user.name}</h1>;
}

async function UserProfile({ userId }: { userId: string }) {
  const user = await getUser(userId);
  return <p>{user.bio}</p>;
}

unstable_cache (Data Cache)

import { unstable_cache } from "next/cache";

const getCachedPosts = unstable_cache(
  async () => {
    return db.post.findMany();
  },
  ["posts"], // Cache key
  {
    revalidate: 3600, // Revalidate every hour
    tags: ["posts"], // Tag for on-demand revalidation
  },
);

// Usage
const posts = await getCachedPosts();

Third-Party Scripts

Analytics (Vercel)

// app/layout.tsx
import { Analytics } from "@vercel/analytics/react";
import { SpeedInsights } from "@vercel/speed-insights/next";

export default function RootLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <html lang="en">
      <body>
        {children}
        <Analytics />
        <SpeedInsights />
      </body>
    </html>
  );
}

External Scripts

import Script from 'next/script';

// Load after page interactive
<Script
  src="https://www.googletagmanager.com/gtag/js?id=GA_ID"
  strategy="afterInteractive"
/>

// Load when browser is idle
<Script
  src="https://widget.example.com/embed.js"
  strategy="lazyOnload"
/>

// Worker thread (experimental)
<Script
  src="https://heavy-analytics.js"
  strategy="worker"
/>

Script Loading Strategies

Strategy	When	Use Case
`beforeInteractive`	Before hydration	Critical polyfills
`afterInteractive`	After hydration	Analytics, chat widgets
`lazyOnload`	Browser idle	Non-critical embeds
`worker`	Web Worker	Heavy analytics (experimental)

Monitoring & Debugging

Web Vitals Reporting

// app/layout.tsx
export function reportWebVitals(metric: {
  id: string;
  name: string;
  startTime: number;
  value: number;
  label: "web-vital" | "custom";
}) {
  // Send to analytics
  if (metric.label === "web-vital") {
    fetch("/api/analytics", {
      method: "POST",
      body: JSON.stringify({
        name: metric.name,
        value: metric.value,
        id: metric.id,
      }),
    });
  }
}

Lighthouse CI

# .github/workflows/lighthouse.yml
name: Lighthouse CI
on: push

jobs:
  lighthouse:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Run Lighthouse
        uses: treosh/lighthouse-ci-action@v10
        with:
          urls: |
            https://yourportfolio.com/
            https://yourportfolio.com/projects
          uploadArtifacts: true
          temporaryPublicStorage: true

Performance Checklist

Pre-Launch

All images use <Image /> component
Fonts use next/font
Dynamic imports for heavy components
Bundle analyzed and optimized
No layout shifts (CLS < 0.1)

Images

All images have explicit dimensions or use fill
Above-the-fold images have priority
Below-the-fold images use lazy loading
sizes prop set for responsive images
WebP/AVIF formats enabled

JavaScript

Tree shaking enabled
Code splitting implemented
Third-party scripts use correct strategy
No render-blocking scripts

Caching

Static pages use ISR where appropriate
API routes cached correctly
Fonts cached with long max-age
Static assets have immutable cache headers

Monitoring

Vercel Analytics enabled
SpeedInsights enabled
Core Web Vitals tracked
Error boundaries in place

Quick Wins

Add priority to hero image - Immediate LCP improvement
Use next/font - Eliminates FOUT/FOIT
Enable optimizePackageImports - Smaller bundles
Add Suspense boundaries - Better perceived performance
Use ISR - Faster TTFB than SSR
Lazy load modals - Reduce initial bundle
Skeleton loaders - Better UX than spinners

name	performance-optimization
description	Optimize Next.js portfolio for Core Web Vitals, bundle size, loading performance, and achieve 90+ Lighthouse scores.
author	Jaivish Chauhan @ GDG SSIT
version	1.0.0
url	https://github.com/JaivishChauhan/vibecoding-starter

name	performance-optimization
description	Optimize Next.js portfolio for Core Web Vitals, bundle size, loading performance, and achieve 90+ Lighthouse scores.
author	Jaivish Chauhan @ GDG SSIT
version	1.0.0
url	https://github.com/JaivishChauhan/vibecoding-starter

performance-optimization

このリポジトリの他の Skills

このリポジトリの他の Skills

Performance Optimization Mastery

Core Philosophy

Core Web Vitals Targets

Image Optimization

Next.js Image Component (Essential)

Image Configuration

Image Best Practices

Font Optimization

Next.js Font System

Font Subsetting

Bundle Optimization

Package Import Optimization

Dynamic Imports (Code Splitting)

Analyze Bundle Size

Import Optimization Patterns

Rendering Strategies

Static Generation (Fastest)

Incremental Static Regeneration (ISR)

On-Demand Revalidation

Loading Performance

Streaming with Suspense

Loading States

Skeleton Component

Preloading & Prefetching

Link Prefetching

Resource Hints

Animation Performance

GPU-Accelerated Properties

Reduce Motion for Accessibility

CSS-Based Animations (Lower Overhead)

Caching Strategies

Fetch Caching

React Cache

unstable_cache (Data Cache)

Third-Party Scripts

Analytics (Vercel)

External Scripts

Script Loading Strategies

Monitoring & Debugging

Web Vitals Reporting

Lighthouse CI

Performance Checklist

Pre-Launch

Images

JavaScript

Caching

Monitoring

Quick Wins

Performance Optimization Mastery

Core Philosophy

Core Web Vitals Targets

Image Optimization

Next.js Image Component (Essential)

Image Configuration

Image Best Practices

Font Optimization

Next.js Font System

Font Subsetting

Bundle Optimization

Package Import Optimization

Dynamic Imports (Code Splitting)

Analyze Bundle Size

Import Optimization Patterns

Rendering Strategies

Static Generation (Fastest)

Incremental Static Regeneration (ISR)

On-Demand Revalidation

Loading Performance

Streaming with Suspense

Loading States

Skeleton Component

Preloading & Prefetching

Link Prefetching

Resource Hints

Animation Performance

GPU-Accelerated Properties

Reduce Motion for Accessibility