Vercel Not Working? Common Errors & Fixes

A failed Vercel deployment almost always has its real cause a few lines above the final 'Command "npm run build" exited with 1' line. Run the same build locally, fix the first red error in the build log, then redeploy without the build cache.

A sitewide 404 after a successful Vercel build usually means the wrong Framework Preset or Output Directory; 404s only on refreshed routes mean a single-page app is missing a rewrite to index.html.

A 504 FUNCTION_INVOCATION_TIMEOUT means your function ran past its max duration (300s default with Fluid compute). Make sure every code path returns a response, move the function region next to your database or API, and raise maxDuration on Pro (up to 800s).

Vercel builds run with 8 GB of memory on the default machine; if your build needs more it is killed with SIGKILL or an out-of-memory error. Raise the Node heap below the limit, cut heavy dependencies, or use a larger build machine on Pro.

Vercel only applies environment variable changes to new deployments, and only to the environments you ticked. Redeploy after every change, check the Production/Preview scope, and remember NEXT_PUBLIC_ variables are baked in at build time.

'Invalid Configuration' means your DNS does not yet match what Vercel expects. Add the exact A record (apex) or CNAME (subdomain) shown in Settings > Domains, delete old conflicting records, and wait for propagation; a TXT record is needed if another Vercel account uses the domain.

Most surprise Vercel bills come from bandwidth over 1 TB, CDN requests, function compute (Active CPU and provisioned memory) or image optimization, often driven by bots or a runaway cron job. Find the line item in Usage, block the source, and set a spend budget with pausing.

On the Hobby plan, deployments from a private repository are blocked when the commit author is not the Vercel account owner. Make sure your Git email/account is linked to Vercel, or upgrade to Pro and add the collaborator.

If pushes stop creating Vercel deployments, check the Ignored Build Step, the Vercel GitHub App's repo access, and the commit status for a 'rate limited' message (Hobby allows 100 deployments a day).

A redirect loop on a Vercel site behind Cloudflare is caused by Cloudflare's SSL mode set to Flexible: Cloudflare calls Vercel over HTTP and Vercel redirects back to HTTPS forever. Set SSL/TLS to Full (or Full strict) or switch the record to DNS only.

FUNCTION_INVOCATION_FAILED (500) means your function crashed: an uncaught exception, unhandled promise rejection or runtime crash. The stack trace in the Logs tab shows the line; missing production environment variables are a frequent trigger.

Vercel Functions reject request or response bodies over 4.5 MB with 413 FUNCTION_PAYLOAD_TOO_LARGE. Upload files directly from the browser to storage (e.g. Vercel Blob client uploads or presigned URLs) and stream or shrink large responses.

A paused Vercel site usually means Spend Management hit your budget (Pro), a Hobby usage limit was exceeded, or a policy issue such as commercial use on Hobby. Each cause has a different fix; check Billing first, then your email.