Next.js 13.5 improves local dev performance and reliability with:

• 22% faster local server startup: Iterate faster with the App & Pages Router
• 29% faster HMR (Fast Refresh): For faster iterations when saving changes
• 40% less memory usage: Measured when running next start
• Optimized Package Imports: Faster updates when using popular icon and component libraries
• next/image Improvements: <picture>, art direction, and dark mode support
• And over 438 bugs patched!

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Improving startup and Fast Refresh time

We're excited to see the continued adoption of the App Router, now growing 80% MoM when looking at the top 10 million origins crawled by the HTTP Archive.

Since Next.js 13.4, our focus has been on improving performance and reliability for App Router applications. Comparing 13.4 to 13.5, we've seen the following improvements on a new application:

• 22% faster local server startup
• 29% faster HMR (Fast Refresh)
• 40% less memory usage

We were able to achieve this performance increase through optimizations like:

• Doing less work by caching or minimizing slow operations
• Optimizing expensive file system operations
• Better incremental tree traversal during compilation
• Moving unnecessary blocking synchronous calls to be lazy
• Automatically configuring large icon libraries

Next.js user Lattice reported between 87-92% faster compilation in their testing.

While we continue to iterate and improve our current bundler performance, we're also working on Turbopack (Beta) in parallel to further increase performance. With 13.5, next dev --turbo now supports more features.

Optimized Package Imports

We've made an exciting breakthrough to optimize package imports, improving both local dev performance and production cold starts, when using large icon or component libraries or other dependencies that re-export hundreds or thousands of modules.

Previously, we added support for modularizeImports, enabling you to configure how imports should resolve when using these libraries. In 13.5, we have superseeded this option with optimizePackageImports, which doesn't require you to specify the mapping of imports, but instead will automatically optimize imports for you.

Libraries like @mui/icons-material, @mui/material, date-fns, lodash, lodash-es, ramda, react-bootstrap, @headlessui/react ,@heroicons/react , and lucide-react are now automatically optimized, only loading the modules you are actually using, while still giving you the convenience of writing import statements with many named exports.

View the PR or learn more about optimizePackageImports in our documentation.

next/image Improvements

Based on community feedback, we've added a new experimental function unstable_getImgProps() to support advanced use cases without using the <Image> component directly, including:

• Working with background-image or image-set
• Working with canvas context.drawImage() or new Image()
• Working with <picture> media queries to implement Art Direction or Light/Dark Mode images

Additionally, the placeholder prop now supports providing arbitrary data:image/ for placeholder images that shouldn't be blurred (demo).

Learn more about next/image in our documentation.

Other Improvements

Since 13.4.0, we've fixed over 438 bugs and made various improvements including:

• [Docs] New documentation on Forms and Mutations
• [Docs] New documentation on Server and Client Components
• [Docs] New documentation on Content Security Policy and Nonces
• [Docs] New documentation on Caching and Revalidating
• [Feature] useParams and useSearchParams from next/navigation now work in the Pages Router for incremental adoption
• [Feature] Support for scroll: false on router.push / router.replace
• [Feature] Support for scroll={false} on next/link
• [Feature] HTTPS support for development: next dev --experimental-https
• [Feature] Added support for cookies().has() (Docs)
• [Feature] Added support for IPv6 hostnames
• [Feature] Added support for Yarn PnP with the App Router
• [Feature] Added support for redirect() in Server Actions
• [Feature] Added support for using Bun with creating projects: bunx create-next-app (Docs)
• [Feature] Draft Mode support for use inside Middleware and the Edge Runtime
• [Feature] cookies() and headers() are now supported inside Middleware
• [Feature] Metadata API now supports summary_large_image in Twitter cards
• [Feature] RedirectType is now exported from next/navigation
• [Feature] Added experimental test mode for Playwright (Docs)
• [Improvement] Refactored next start to handle 1062% more requests/second
• [Improvement] Optimized Next.js internals to improve cold starts (up to 40% faster, tested on Vercel)
• [Improvement] Better Jest support for the App Router (PR)
• [Improvement] Redesigned next dev output (PR)
• [Improvement] Server Actions now work with fully static routes (including revalidating data with ISR)
• [Improvement] Server Actions no longer block navigation between routes
• [Improvement] Server Actions can no longer trigger multiple concurrent actions
• [Improvement] Server Actions calling redirect() now push into the history stack instead of replacing the current entry to ensure the back button works
• [Improvement] Server Actions add no-cache, no-store cache-control header to prevent browser caching
• [Improvement] Fixed a bug where Server Actions could be called twice after navigating
• [Improvement] Improved support for Emotion CSS with Server Components
• [Improvement] Support for scroll-behavior: smooth for hash url changes
• [Improvement] Added polyfill for Array.prototype.at in all browsers
• [Improvement] Fixed race condition in next dev cache when handling multiple parallel requests
• [Improvement] fetch output in console now shows requests that skipped cache with cache: SKIP
• [Improvement] usePathname now properly strips basePath
• [Improvement] next/image now properly preloads images in App Router
• [Improvement] not-found no longer renders the root layout twice
• [Improvement] NextRequest can now be cloned (i.e new NextRequest(request))
• [Improvement] app/children/page.tsx now properly works for literal /children routes
• [Improvement] Content Security Policy now supports nonce for preinitialized scripts
• [Improvement] Using redirect from next/navigation now supports basePath
• [Improvement] Fixed process.env not being available during rendering in output: 'standalone' mode
• [Improvement] Improved error message when using a Static Export with unsupported features
• [Improvement] Improved recursive readdir implementation (~3x faster)
• [Improvement] Fixed fallback: false with dynamic route segments previously causing hanging requests
• [Improvement] Fixed error where signal was passed to revalidate requests, causing them to fail when the request was already aborted
• [Improvement] Removed fetch polling on 404 page in favor of websocket events, preventing unnecessary reloads when running next dev
• [Improvement] performance.measure no longer can cause a hydration mismatch
• [Improvement] Fixed cases where an unexpected full reload could happen editing pages/_app
• [Improvement] ImageResponse now extends Response for improved type checking (PR)
• [Improvement] pages is no longer shown when there is no pages output in next build
• [Improvement] Fixed skipTrailingSlashRedirect being ignored in <Link>
• [Improvement] Fixed duplicated dynamic metadata routes in dev mode

Contributors

Next.js is the result of the combined work of over 2,800 individual developers, industry partners like Google and Meta, and our core team at Vercel. Join the community on GitHub Discussions, Reddit, and Discord.

This release was brought to you by:

• The Next.js team: Andrew, Balazs, Jiachi, Jimmy, JJ, Josh, Sebastian, Shu, Steven, Tim, Wyatt, and Zack.
• The Turbopack team: Donny, Justin, Leah, Maia, OJ, Tobias, and Will.

And the contributions of: @opnay, @vinaykulk621, @goguda, @coreyleelarson, @bencmbrook, @cramforce, @williamli, @stefanprobst, @feugy, @Kikobeats, @dvoytenko, @MaxLeiter, @devjiwonchoi, @lacymorrow, @kylemcd, @tibi1220, @iamarpitpatidar, @pythagoras-yamamoto, @alexkirsz, @jsteele-stripe, @tknickman, @gaojude, @janicklas-ralph, @ericfennis, @JohnAdib, @MiLk, @delbaoliveira, @leerob, @LuudJanssen, @lucasconstantino, @davecarlson, @colinhacks, @jantimon, @Banbarashik, @ForsakenHarmony, @arturbien, @gnoff, @hsrvms, @DuCanhGH, @tim-hanssen, @Aryan9592, @rishabhpoddar, @Lantianyou, @joulev, @AkifumiSato, @trigaten, @HurSungYun, @DevLab2425, @SukkaW, @daniel-web-developer, @ky1ejs, @wyattjoh, @ShaunFerris, @syedtaqi95, @Heidar-An, @Jeffrey-Zutt, @Ryan-Dia, @steppefox, @hiro0218, @rjsdnql123, @fgiuliani, @steven-tey, @AntoineBourin, @adamrhunter, @darshanjain-entrepreneur, @s0h311, @djreillo, @dijonmusters, @cassidoo, @anonrig, @gfgabrielfranca, @Bitbbot, @BrennanColberg, @Nick-Mazuk, @thomasballinger, @lucgagan, @nroland013, @SonMooSans, @jenewland1999, @thorwebdev, @jyunhanlin, @Gnadhi, @yagogmaisp, @carlos-menezes, @ryo-manba, @vamcs, @matepapp, @SleeplessOne1917, @ecklf, @karlhorky, @starunaway, @FernandVEYRIER, @Terro216, @anthonyshew, @suhaotian, @simonswiss, @feikerwu, @lubakravche, @masnormen, @bottxiang, @mhmdrioaf, @tyler-lutz, @vincenthongzy, @yigithanyucedag, @doinki, @danger-ahead, @bre30kra69cs, @Yash-Singh1, @krmeda, @bigyanse, @2-NOW, @Mingyu-Song, @morganfeeney, @aralroca, @nickmccurdy, @adamjmcgrath, @angel1254mc, @cxa, @ibash, @mohanraj-r, @kevinmitch14, @iaurg, @steebchen, @Cow258, @charlesbdudley, @tyhopp, @Drblessing, @milovangudelj, @jacobsfletch, @JoshuaKGoldberg, @zignis, @ChristianIvicevic, @mrxbox98, @oliviertassinari, @fsansalvadore, @tvthatsme, @dvakatsiienko, @brunoeduardodev, @sonam-serchan, @vicsantizo, @leodr, @wiscaksono, @hustLer2k, @joshuabaker, @shozibabbas, @omarhoumz, @jamespearson, @tristndev, @AldeonMoriak, @manovotny, @mirismaili, @SuttonJack, @jeremydouglas, @JanCizmar, @mltsy, @WilderDev, @Guilleo03, @Willem-Jaap, @escwxyz, @wiredacorn, @Ethan-Arrowood, @BaffinLee, @greatSumini, @ciruz, @kijikunnn, @DustinsCode, @riqwan, @joostdecock, @nikolovlazar, @Bowens20832, @JohnAlbin, @gidgudgod, @maxproske, @dunklesToast, @yyuemii, @mPaella, @mknichel, @niko20, @mkcy3, @valentinpolitov, @smaeda-ks, @keyz, @Schniz, @koba04, @jiwooIncludeJeong, @ethanmick, @didemkkaslan, @itsmingjie, @v1k1, @thepatrick00, @taylorbryant, @kvnang, @alainkaiser, @simPod, @svarunid, @pauek, @lycuid, @MarkAtOmniux, @darshkpatel, @johnta0, @devagrawal09, @ibrahemid, @JesseKoldewijn, @javivelasco, @05lazy, @alexanderbluhm, @Fonger, @souporserious, @DevEsteves, @sanjaiyan-dev, @g12i, @cesarkohl, @josh, @li-jia-nan, @gabschne, @akd-io, @runjuu, @jocarrd, @nnnnoel, @ferdingler, and @ikryvorotenko