No,Category,Guideline,Description,Do,Don't,Code Good,Code Bad,Severity,Docs URL
1,Routing,Use App Router for new projects,App Router is the recommended approach in Next.js 14+,app/ directory with page.tsx,pages/ for new projects,app/dashboard/page.tsx,pages/dashboard.tsx,Medium,https://nextjs.org/docs/app
2,Routing,Use file-based routing,Create routes by adding files in app directory,page.tsx for routes layout.tsx for layouts,Manual route configuration,app/blog/[slug]/page.tsx,Custom router setup,Medium,https://nextjs.org/docs/app/building-your-application/routing
3,Routing,Colocate related files,Keep components styles tests with their routes,Component files alongside page.tsx,Separate components folder,app/dashboard/_components/,components/dashboard/,Low,
4,Routing,Use route groups for organization,Group routes without affecting URL,Parentheses for route groups,Nested folders affecting URL,(marketing)/about/page.tsx,marketing/about/page.tsx,Low,https://nextjs.org/docs/app/building-your-application/routing/route-groups
5,Routing,Handle loading states,Use loading.tsx for route loading UI,loading.tsx alongside page.tsx,Manual loading state management,app/dashboard/loading.tsx,useState for loading in page,Medium,https://nextjs.org/docs/app/building-your-application/routing/loading-ui-and-streaming
6,Routing,Handle errors with error.tsx,Catch errors at route level,error.tsx with reset function,try/catch in every component,app/dashboard/error.tsx,try/catch in page component,High,https://nextjs.org/docs/app/building-your-application/routing/error-handling
7,Rendering,Use Server Components by default,Server Components reduce client JS bundle,Keep components server by default,Add 'use client' unnecessarily,export default function Page(),('use client') for static content,High,https://nextjs.org/docs/app/building-your-application/rendering/server-components
8,Rendering,Mark Client Components explicitly,'use client' for interactive components,Add 'use client' only when needed,Server Component with hooks/events,('use client') for onClick useState,No directive with useState,High,https://nextjs.org/docs/app/building-your-application/rendering/client-components
9,Rendering,Push Client Components down,Keep Client Components as leaf nodes,Client wrapper for interactive parts only,Mark page as Client Component,<InteractiveButton/> in Server Page,('use client') on page.tsx,High,
10,Rendering,Use streaming for better UX,Stream content with Suspense boundaries,Suspense for slow data fetches,Wait for all data before render,<Suspense><SlowComponent/></Suspense>,await allData then render,Medium,https://nextjs.org/docs/app/building-your-application/routing/loading-ui-and-streaming
11,Rendering,Choose correct rendering strategy,SSG for static SSR for dynamic ISR for semi-static,generateStaticParams for known paths,SSR for static content,export const revalidate = 3600,fetch without cache config,Medium,
12,DataFetching,Fetch data in Server Components,Fetch directly in async Server Components,async function Page() { const data = await fetch() },useEffect for initial data,const data = await fetch(url),useEffect(() => fetch(url)),High,https://nextjs.org/docs/app/building-your-application/data-fetching
13,DataFetching,Configure caching explicitly (Next.js 15+),Next.js 15 changed defaults to uncached for fetch,Explicitly set cache: 'force-cache' for static data,Assume default is cached (it's not in Next.js 15),fetch(url { cache: 'force-cache' }),fetch(url) // Uncached in v15,High,https://nextjs.org/docs/app/building-your-application/upgrading/version-15
14,DataFetching,Deduplicate fetch requests,React and Next.js dedupe same requests,Same fetch call in multiple components,Manual request deduplication,Multiple components fetch same URL,Custom cache layer,Low,
15,DataFetching,Use Server Actions for mutations,Server Actions for form submissions,action={serverAction} in forms,API route for every mutation,<form action={createPost}>,<form onSubmit={callApiRoute}>,Medium,https://nextjs.org/docs/app/building-your-application/data-fetching/server-actions-and-mutations
16,DataFetching,Revalidate data appropriately,Use revalidatePath/revalidateTag after mutations,Revalidate after Server Action,'use client' with manual refetch,revalidatePath('/posts'),router.refresh() everywhere,Medium,https://nextjs.org/docs/app/building-your-application/caching#revalidating
17,Images,Use next/image for optimization,Automatic image optimization and lazy loading,<Image> component for all images,<img> tags directly,<Image src={} alt={} width={} height={}>,<img src={}/>,High,https://nextjs.org/docs/app/building-your-application/optimizing/images
18,Images,Provide width and height,Prevent layout shift with dimensions,width and height props or fill,Missing dimensions,<Image width={400} height={300}/>,<Image src={url}/>,High,
19,Images,Use fill for responsive images,Fill container with object-fit,fill prop with relative parent,Fixed dimensions for responsive,"<Image fill className=""object-cover""/>",<Image width={window.width}/>,Medium,
20,Images,Configure remote image domains,Whitelist external image sources,remotePatterns in next.config.js,Allow all domains,remotePatterns: [{ hostname: 'cdn.example.com' }],domains: ['*'],High,https://nextjs.org/docs/app/api-reference/components/image#remotepatterns
21,Images,Use priority for LCP images,Mark above-fold images as priority,priority prop on hero images,All images with priority,<Image priority src={hero}/>,<Image priority/> on every image,Medium,
22,Fonts,Use next/font for fonts,Self-hosted fonts with zero layout shift,next/font/google or next/font/local,External font links,import { Inter } from 'next/font/google',"<link href=""fonts.googleapis.com""/>",Medium,https://nextjs.org/docs/app/building-your-application/optimizing/fonts
23,Fonts,Apply font to layout,Set font in root layout for consistency,className on body in layout.tsx,Font in individual pages,<body className={inter.className}>,Each page imports font,Low,
24,Fonts,Use variable fonts,Variable fonts reduce bundle size,Single variable font file,Multiple font weights as files,Inter({ subsets: ['latin'] }),Inter_400 Inter_500 Inter_700,Low,
25,Metadata,Use generateMetadata for dynamic,Generate metadata based on params,export async function generateMetadata(),Hardcoded metadata everywhere,generateMetadata({ params }),export const metadata = {},Medium,https://nextjs.org/docs/app/building-your-application/optimizing/metadata
26,Metadata,Include OpenGraph images,Add OG images for social sharing,opengraph-image.tsx or og property,Missing social preview images,opengraph: { images: ['/og.png'] },No OG configuration,Medium,
27,Metadata,Use metadata API,Export metadata object for static metadata,export const metadata = {},Manual head tags,export const metadata = { title: 'Page' },<head><title>Page</title></head>,Medium,
28,API,Use Route Handlers for APIs,app/api routes for API endpoints,app/api/users/route.ts,pages/api for new projects,export async function GET(request),export default function handler,Medium,https://nextjs.org/docs/app/building-your-application/routing/route-handlers
29,API,Return proper Response objects,Use NextResponse for API responses,NextResponse.json() for JSON,Plain objects or res.json(),return NextResponse.json({ data }),return { data },Medium,
30,API,Handle HTTP methods explicitly,Export named functions for methods,Export GET POST PUT DELETE,Single handler for all methods,export async function POST(),switch(req.method),Low,
31,API,Validate request body,Validate input before processing,Zod or similar for validation,Trust client input,const body = schema.parse(await req.json()),const body = await req.json(),High,
32,Middleware,Use middleware for auth,Protect routes with middleware.ts,middleware.ts at root,Auth check in every page,export function middleware(request),if (!session) redirect in page,Medium,https://nextjs.org/docs/app/building-your-application/routing/middleware
33,Middleware,Match specific paths,Configure middleware matcher,config.matcher for specific routes,Run middleware on all routes,matcher: ['/dashboard/:path*'],No matcher config,Medium,
34,Middleware,Keep middleware edge-compatible,Middleware runs on Edge runtime,Edge-compatible code only,Node.js APIs in middleware,Edge-compatible auth check,fs.readFile in middleware,High,
35,Environment,Use NEXT_PUBLIC prefix,Client-accessible env vars need prefix,NEXT_PUBLIC_ for client vars,Server vars exposed to client,NEXT_PUBLIC_API_URL,API_SECRET in client code,High,https://nextjs.org/docs/app/building-your-application/configuring/environment-variables
36,Environment,Validate env vars,Check required env vars exist,Validate on startup,Undefined env at runtime,if (!process.env.DATABASE_URL) throw,process.env.DATABASE_URL (might be undefined),High,
37,Environment,Use .env.local for secrets,Local env file for development secrets,.env.local gitignored,Secrets in .env committed,.env.local with secrets,.env with DATABASE_PASSWORD,High,
38,Performance,Analyze bundle size,Use @next/bundle-analyzer,Bundle analyzer in dev,Ship large bundles blindly,ANALYZE=true npm run build,No bundle analysis,Medium,https://nextjs.org/docs/app/building-your-application/optimizing/bundle-analyzer
39,Performance,Use dynamic imports,Code split with next/dynamic,dynamic() for heavy components,Import everything statically,const Chart = dynamic(() => import('./Chart')),import Chart from './Chart',Medium,https://nextjs.org/docs/app/building-your-application/optimizing/lazy-loading
40,Performance,Avoid layout shifts,Reserve space for dynamic content,Skeleton loaders aspect ratios,Content popping in,"<Skeleton className=""h-48""/>",No placeholder for async content,High,
41,Performance,Use Partial Prerendering,Combine static and dynamic in one route,Static shell with Suspense holes,Full dynamic or static pages,Static header + dynamic content,Entire page SSR,Low,https://nextjs.org/docs/app/building-your-application/rendering/partial-prerendering
42,Link,Use next/link for navigation,Client-side navigation with prefetching,"<Link href=""""> for internal links",<a> for internal navigation,"<Link href=""/about"">About</Link>","<a href=""/about"">About</a>",High,https://nextjs.org/docs/app/api-reference/components/link
43,Link,Prefetch strategically,Control prefetching behavior,prefetch={false} for low-priority,Prefetch all links,<Link prefetch={false}>,Default prefetch on every link,Low,
44,Link,Use scroll option appropriately,Control scroll behavior on navigation,scroll={false} for tabs pagination,Always scroll to top,<Link scroll={false}>,Manual scroll management,Low,
45,Config,Use next.config.js correctly,Configure Next.js behavior,Proper config options,Deprecated or wrong options,images: { remotePatterns: [] },images: { domains: [] },Medium,https://nextjs.org/docs/app/api-reference/next-config-js
46,Config,Enable strict mode,Catch potential issues early,reactStrictMode: true,Strict mode disabled,reactStrictMode: true,reactStrictMode: false,Medium,
47,Config,Configure redirects and rewrites,Use config for URL management,redirects() rewrites() in config,Manual redirect handling,redirects: async () => [...],res.redirect in pages,Medium,https://nextjs.org/docs/app/api-reference/next-config-js/redirects
48,Deployment,Use Vercel for easiest deploy,Vercel optimized for Next.js,Deploy to Vercel,Self-host without knowledge,vercel deploy,Complex Docker setup for simple app,Low,https://nextjs.org/docs/app/building-your-application/deploying
49,Deployment,Configure output for self-hosting,Set output option for deployment target,output: 'standalone' for Docker,Default output for containers,output: 'standalone',No output config for Docker,Medium,https://nextjs.org/docs/app/building-your-application/deploying#self-hosting
50,Security,Sanitize user input,Never trust user input,Escape sanitize validate all input,Direct interpolation of user data,DOMPurify.sanitize(userInput),dangerouslySetInnerHTML={{ __html: userInput }},High,
51,Security,Use CSP headers,Content Security Policy for XSS protection,Configure CSP in next.config.js,No security headers,headers() with CSP,No CSP configuration,High,https://nextjs.org/docs/app/building-your-application/configuring/content-security-policy
52,Security,Validate Server Action input,Server Actions are public endpoints,Validate and authorize in Server Action,Trust Server Action input,Auth check + validation in action,Direct database call without check,High,