404: NOT_FOUND Code: DEPLOYMENT_NOT_FOUND

404: NOTFOUND Code: DEPLOYMENTNOT_FOUND (Vercel)

TL;DR: Vercel is telling you it has no deployment attached to that hostname. Your DNS works, but the domain is not assigned to any project, or the deployment behind the URL is gone. Fix it in the dashboard: Settings -> Domains -> add the domain to the project, or open the Deployments tab and promote a Ready build to Production. No code change needed.

404: NOT_FOUND
Code: DEPLOYMENT_NOT_FOUND
ID: cpt1::abc-123

1. Read the code, not just the 404

Vercel prints two different 404s and they mean different things:

• NOT_FOUND: a deployment IS serving, but its route table has no match for your URL. That is a routing/build-output problem.
• DEPLOYMENT_NOT_FOUND: no deployment is attached to the hostname at all. That is a domain/project problem, and it is this skill.

Expected: you confirm the page shows DEPLOYMENT_NOT_FOUND.

2. Attach the domain to the project

In the Vercel dashboard, open your project -> Settings -> Domains. Type the domain (e.g. carbcleantruckcheck.app) and click Add. It takes effect within seconds; you do not need to redeploy.

Expected: refreshing the URL loads your site instead of the error page.

3. Check you are opening the right URL

Preview URLs (project-git-branch-team.vercel.app) are ephemeral: they die when the branch or project is deleted. The production domain (project.vercel.app or your custom domain) is the stable one. If you bookmarked a preview URL months ago, that is your 404.

Expected: the production URL from the latest deployment's Visit button works.

4. Confirm a Ready production deployment exists

Open the Deployments tab. If the latest Production deployment shows Error or Canceled, there is nothing to serve: fix the build error first, then redeploy. If a good build exists but is not Production, promote it.

Expected: Deployments tab shows a Ready build marked Production.

When this applies

• The Vercel error page shows Code: DEPLOYMENT_NOT_FOUND
• Custom domain added but never attached to the project, or project renamed
• Old preview/deployment URL that no longer exists

When it does not apply

• Code: NOT_FOUND without DEPLOYMENT_: routing or output-directory issue, different fix
• Your app renders its own 404 page: that is your code, not Vercel
• Build failures in the deploy log: fix the build first

Compatibility

All Vercel plans. Applies to *.vercel.app domains and custom domains alike. Dashboard steps are the same on Hobby, Pro, and Enterprise.

Why it happens

Vercel routes each hostname to a specific deployment. If the domain was never added under the project's Domains settings, was removed, or the deployment the URL pointed at was deleted, the edge has nowhere to send the request and returns this code. Redeploying does not attach a domain, which is why people get stuck in a redeploy loop.

Edge cases

• Domain shows as assigned but still 404s: DNS may still be propagating (up to 24h), or the domain is assigned to a different project/team.
• project.vercel.app taken by someone else: pick another name or rename the project so the default slug is free.
• Deployment Protection on: deployment URLs ask for a Vercel login by design; that is not DEPLOYMENTNOTFOUND, use the production domain instead.

Multiple real deployment writeups document this exact failure. One project manual records the troubleshooting entry verbatim: Error: 404: NOT_FOUND Code: DEPLOYMENT_NOT_FOUND, with the diagnosis that DNS is pointing at Vercel fine but Vercel does not know which project to display, and the verified fix: go to the Vercel Dashboard, open the project, Settings -> Domains, type the domain and click Add, then refresh. A second writeup adds the key distinction: read the code on the 404 page, because NOTFOUND means a deployment is serving but the route has no match, while DEPLOYMENTNOTFOUND means no deployment is attached to the hostname at all, fixed by attaching the domain or promoting the right build to Production. Full threads: https://github.com/bgillis99-pixel/final-125111am/blob/HEAD/DEPLOYMENTMANUAL.md and https://github.com/sakshamfit/restaurant/blob/HEAD/DEPLOY.md