AI & TechnologyNext.js and Web Build Errors: 8 Fixes (2026)

Short answer: web app errors split into build failures, where next build or npm run build stops, and runtime errors, where the deployed site breaks in the browser or on the server. Find your error below; each one links to a full fix page checked against the Next.js, Vite, Node.js or Netlify documentation.

Next.js and web build errors are easiest to fix once you know whether the build, the browser or the server threw them. The 8 errors below stop web apps from building or working after deploy, including apps generated by AI builders. Facts about each tool come from its own documentation, as checked on the linked fix page; the advice on what to do and in which order is App369’s.

Next.js errors when a page renders

These two errors appear when a page renders, in the browser console or the server log. Each names what didn’t match: the HTML, or the image host.

Hydration error: the server HTML didn’t match

Something renders differently on the server and in the browser: a read of window, localStorage or the time during render, invalid HTML nesting, or a browser extension. On iPhone, according to the Next.js hydration docs, “iOS attempts to detect phone numbers, email addresses, and other data in text content and convert them into links, leading to hydration mismatches.” Full steps: Next.js hydration error.

Image error: the hostname isn’t configured

The image comes from a host that isn’t in images.remotePatterns. The Next.js docs say “Hostname: example.org is different from www.example.org and from subdomains like assets.example.org”, so list each host exactly, with its protocol, port and path. Full steps: Next.js image unconfigured host.

Next.js errors on the server or at build time

These three come from how a page reads request data or receives uploads. The error message names the function involved.

“useSearchParams() should be wrapped in a suspense boundary”

The Next.js docs say “Reading search parameters through useSearchParams() without a Suspense boundary will opt the entire page into client-side rendering.” Wrap the smallest component that reads it in Suspense, or keep the page a Server Component. Full steps: useSearchParams Suspense boundary.

“DynamicServerError: Dynamic Server Usage”

cookies() or headers() ran outside the render it belongs to: inside a timer, or in a promise nobody awaited. The Next.js docs describe the timer case as “The function was called inside of a setTimeout or setInterval, causing the value to be read outside of the call stack that the context was bound to.” Read the values first and await every helper that uses them. Full steps: Next.js Dynamic Server Usage.

Server Action fails on uploads over 1 MB

According to the Next.js serverActions docs, “By default, the maximum size of the request body sent to a Server Action is 1MB.” Raise bodySizeLimit with room to spare. On Vercel, files over 4.5 MB should go from the browser straight to storage. Full steps: Next.js Server Action body size limit.

Vite, Node.js and Netlify

These three errors appear in Vite apps, Node.js builds and Netlify Functions. Each is a mismatch between the app and where it runs.

Vite: “Failed to load module script” (MIME type text/html)

The browser asked for a JavaScript file and got an HTML page. After a deploy, according to Vite’s build docs, “the hosting service may delete the assets from previous deployments,” so old HTML asks for files that are gone. Check the catch-all rewrite to index.html and the base setting too. Full steps: Vite failed to load module script.

Node.js “ERR_OSSL_EVP_UNSUPPORTED”

The Node.js 17 release notes say “it’s likely that your application or a module you’re using is attempting to use an algorithm or key size which is no longer allowed by default with OpenSSL 3.0.” Upgrade the build tooling; --openssl-legacy-provider is a temporary workaround. Full steps: Node.js ERR_OSSL_EVP_UNSUPPORTED.

Netlify Function times out

Netlify lists a 60-second limit for synchronous functions and doesn’t mark it as configurable. Time out each outside call, move the function’s region near the database on a Pro or Enterprise plan, or run long work as a background function, which per Netlify’s docs returns “an initial 202 success response” straight away. Full steps: Netlify Function timeout.

Which to check first

The fastest route is the first error in the build log or the browser console, with the file and line it names. App369’s full order for a web app that just broke:

1. Note where it fails: next build or npm run build, the browser console, or a server or function log.
2. Run the production build locally, where a build error is faster to read and fix.
3. For a browser error, test in a private window with extensions off.
4. For a server error, find the function the message names (cookies(), useSearchParams(), a Server Action) and read how it is called.
5. Check what changed since the last good deploy: packages, Node.js version, config.

The Vercel and Next.js errors page lists every fix for both. For deploy and function errors on Vercel, see the Vercel errors guide.

Need a hand?

App369 fixes single web build and runtime bugs at a fixed price. If one bug is the whole problem, the App Fix Ticket covers it in two fixed-price steps: a $450 diagnosis that finds the root cause and gives you a fixed quote for the fix, then the fix itself. If the app was built with an AI builder and more is going on, the AI-Built App Rescue starts with a Launch Check of the whole app. Or describe the problem and get a written quote.