My deploy keeps failing. What do I do?

Also searched as: Vercel build failed · Vercel build error · Netlify build failed · Netlify build command failed · Deploy failed

Updated 3 October 2026

Short answer

Open the build log and find the first error, not the last line. Most failed deploys come down to one of four things: the host builds with a different Node version from your laptop, the dependency lockfile doesn't match package.json, a setting the build needs isn't set on the host, or the host treats a warning as an error. Build it on your own machine the way the host does, and it will usually fail the same way.

What's the problem

You push the code and the deploy fails: "Build failed", "Command exited with 1", "npm install exited with 1". The site stays on the old version, or never appears at all. Locally, the same code builds fine.

Why it happens

  • A different Node version. The host builds with whatever Node version it has by default, unless the project says otherwise. Code and packages written for one version can fail on another.
  • The lockfile doesn't match. When a build installs dependencies with npm ci, it installs exactly what package-lock.json lists, and stops with an error if that file disagrees with package.json. npm install on your laptop updates the lockfile instead, so you never see the problem.
  • A setting is missing at build time. Frontend tools bake settings such as API addresses into the app while it's being built. If the setting isn't in the host's environment variables, the build fails, or worse, succeeds with a blank.
  • The build server is stricter. Build servers commonly set an environment variable called CI. When it's set, some tools, Create React App among them, fail the build on warnings they'd only print on your laptop.
  • Capital letters in file names. Most hosts build on Linux, where Header.js and header.js are different files.

How to fix it

  1. Open the build log. On Vercel it's on the deployment's page; on Netlify, under the failed deploy. Scroll up to the first line that says error. Everything after it is usually a consequence.
  2. Build it locally the host's way. Delete node_modules, run npm ci, then the exact build command the host uses.
  3. Pin the Node version. Set it in the host's settings, or in the project (an .nvmrc file or the engines field in package.json), so laptop and host match.
  4. If npm ci complains about the lockfile, run npm install locally, check the app still works, and commit the updated package-lock.json.
  5. Add missing build settings in the host's environment variables, then redeploy. Values are baked in at build time, so changing them needs a new build.
  6. Fix the warnings the build is failing on, rather than switching the check off.
  7. Match file-name capitals in every import.

When to call Preventionlabs

If the log names a missing setting or a version, fix it and redeploy. Call us when the build fails because the project has drifted: dependencies years out of date, packages that no longer install, a build tool that's been retired, and every fix uncovering the next failure. The first thing a resurrection delivers is an app that builds and starts on maintained dependencies, deployed in your own hosting account.

Submit your project for a free assessment

Free assessment. $10,000 AUD flat to get it live, only if we take it on and you go ahead.

Sources

  1. Vercel: Troubleshooting Build Errorshosting platform docsIf your build fails, Vercel will report the error message on the Deployments page so that you can investigate and fix the underlying issue.
  2. Netlify: Manage build dependencieshosting platform docsA build’s Node.js version is initially determined by the default version preinstalled on the site’s selected build image.
  3. npm: npm ciofficial docsIf dependencies in the package lock do not match those in package.json, npm ci will exit with an error, instead of updating the package lock.
  4. Create React App: Running Tests: Continuous Integrationofficial docsPopular CI servers already set the environment variable CI by default but you can do this yourself too:
  5. Vite: Env Variables and Modesbuild tool docsThe values of these variables are bundled into your source code at build time.

Related

My app works on my computer but not online. Why? The server isn't your computer. One of five things differs: settings, addresses, the database, the port, or file names. Here's how to find which. npm install fails on my old project. How do I fix it? Usually Node is too new for the project, the lockfile and package.json disagree, or a package needs build tools or no longer exists. Check each, in this order. My project only runs on an old version of Node. What do I do? Run it on its old version with a version manager so it works again, then upgrade one long-term-support release at a time. Node 20 and older are end of life. My site is a blank white page after deploying. Why? The page loaded but the app inside it didn't start. Usually its files are fetched from the wrong path, a setting was blank at build, or routing isn't set up.
← All of Getting it live