GitHub Actions "Unable to resolve action ... unable to find version" in CI

By Kaveh Alemi·Latchkey

A uses: owner/action@ref must resolve to a real tag, branch, or commit in the action repository. A typo, a deleted tag, or a moved major version makes the runner unable to find that ref.

What this error means

The step fails with "Unable to resolve action owner/action@ref, unable to find version ref" before the action runs.

Error: Unable to resolve action `actions/checkout@v99`,
unable to find version `v99`

Common causes

The tag or version does not exist

A pin like @v99 or a misspelled tag has no matching ref in the action repo.

A moving major tag was removed

An action dropped or renamed a major tag, so an old @vN no longer resolves.

How to fix it

Pin to a real released version

1. Check the action repo releases or tags for valid refs.
2. Update uses: to an existing tag or a full commit SHA.
3. Re-run.

# pin to a real tag or a full SHA
- uses: actions/checkout@v4
- uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11

Prefer a full SHA for stability

Pinning to a commit SHA avoids breakage when an action moves or deletes tags.

How to prevent it

• Pin actions to existing tags or full SHAs.
• Watch for action major-version changes in release notes.
• Use Dependabot to keep action refs current.

Frequently asked questions

Related guides

References

• GitHub Actions documentation
• Workflow syntax for GitHub Actions