GitHub Actions actions/download-artifact "Unable to download artifact"

actions/download-artifact@v4 downloads artifacts scoped to the current run by default. A wrong name, an artifact that was never uploaded, or a cross-run download missing run-id/github-token all fail to find the artifact.

What this error means

A download-artifact step fails saying it could not download the artifact, or that no artifact matching the name was found for the run.

github-actions

Error: Unable to download artifact(s): Artifact not found for name: build-output
Please ensure that your artifact is not expired and the artifact was uploaded.

Common causes

Name mismatch or upload skipped

The download name must match the upload name exactly, and the upload step must have actually produced an artifact.

Cross-run download without run-id/token

Downloading an artifact from another workflow run needs run-id, repository, and a github-token.

How to fix it

Match the name or set cross-run inputs

Use the exact artifact name from the upload step.
For a different run, set run-id, github-token, and repository.
Remember v4 artifacts are not visible to v3 download and vice versa.

.github/workflows/ci.yml

- uses: actions/download-artifact@v4
  with:
    name: build-output
    run-id: ${{ github.event.workflow_run.id }}
    github-token: ${{ secrets.GITHUB_TOKEN }}

How to prevent it

Keep upload and download artifact names identical.
Do not mix upload-artifact v3 and download-artifact v4 across the same artifact.