Why are my preview deployments failing in GitHub Actions?

Preview deployments in GitHub Actions usually fail for a handful of common reasons. The exact cause depends on your workflow logs, but here are the most likely issues to check first:

1) Missing or incorrect secrets

Your deployment step may rely on secrets such as:

• GITHUB_TOKEN
• cloud provider credentials
• API keys for your hosting platform

Check:

• the secret names in your workflow match exactly
• the secrets exist in the repo/org settings
• the workflow has permission to read them

2) Insufficient GitHub Actions permissions

If you’re deploying to GitHub Pages, environments, or creating PR comments, the workflow may need explicit permissions, such as:

permissions:
  contents: read
  pull-requests: write
  id-token: write

3) Environment protection rules blocking deployment

If you use GitHub Environments, deployments may be waiting for:

• required reviewers
• branch restrictions
• manual approval

Check the Environment tab in your repo settings.

4) Build failures before deployment

Sometimes the “deployment” fails because the app never built successfully:

• dependency install errors
• test failures
• missing build output
• wrong Node/Python version
• incompatible package lockfile

Look earlier in the logs for the first actual error.

5) Wrong build artifact path

If your deploy step expects a folder like dist/, build/, or .next/, but your build produces something else, deployment will fail.

Example:

- name: Build
  run: npm run build

- name: Deploy
  uses: some/deploy-action@v1
  with:
    path: ./dist

Make sure path matches the actual output directory.

6) Preview URL or PR comment step failing

Some preview workflows fail when:

• the action can’t post a PR comment
• the pull request comes from a fork
• the token doesn’t have permission to write comments
• the deployment URL is invalid or missing

7) Branch / event mismatch

Your workflow may only run on:

• push to main
• pull_request on certain branches

If preview deployments are expected on PRs, confirm the workflow is triggered by:

on:
  pull_request:

8) Deployment platform errors

If you deploy to Vercel, Netlify, Cloudflare Pages, AWS, etc., the platform itself may be rejecting the deployment because of:

• invalid project ID
• expired token
• wrong team/account
• rate limits
• failed environment configuration

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Best next step

Paste the workflow YAML and the exact error message from the Actions log. The first failing step usually points directly to the problem, and I can help you pinpoint it quickly.