How to fix npm ERR! git clone git://github.com/user/repo.git failed npm ERR! fatal: repository not found in npm

Check your package.json and verify the git URL is correct:

Valid formats:
- GitHub: https://github.com/OWNER/REPO or git+https://github.com/OWNER/REPO.git
- SSH: git+ssh://[email protected]/OWNER/REPO.git
- Shorthand: github:OWNER/REPO

Invalid formats (remove if present):
- https://github.com/OWNER/REPO/tree/main (branch reference for UI, not git)
- git://github.com/OWNER/REPO (git:// protocol may be blocked)

Check exact capitalization and spelling.

Visit the repository URL in a web browser to confirm:
- The repository exists and hasn't been deleted
- You can access it (may require login for private repos)
- The owner and repository names are spelled correctly

For GitHub: https://github.com/OWNER/REPO

Check the exact capitalization against the URL in your package.json.

Try cloning the repository manually:

git clone https://github.com/OWNER/REPO.git

If this succeeds, the issue is npm-specific.
If this fails with "repository not found", it's a git/authentication issue.

For SSH URLs:

ssh -T [email protected]

This should respond with "Hi username! You've successfully authenticated."

Private repositories require proper authentication:

Option A: Use Personal Access Token (HTTPS)

{
  "dependencies": {
    "my-package": "git+https://TOKEN:[email protected]/OWNER/REPO.git"
  }
}

Option B: Use SSH with Deploy Keys
1. Add an SSH key as a deploy key in repository settings
2. Configure ~/.ssh/config
3. Update package.json:

{
  "dependencies": {
    "my-package": "git+ssh://[email protected]/OWNER/REPO.git"
  }
}

Outdated cached credentials can cause "repository not found" errors:

Windows:
1. Open Control Panel > Credential Manager
2. Find entries for github.com
3. Delete git-related credentials
4. Run npm install again

macOS:
1. Open Keychain Access
2. Search for "github"
3. Delete expired/incorrect credentials

Linux:

git config --global --unset credential.helper

If git:// URLs fail but https:// works, configure git to use HTTPS:

git config --global url."https://github.com/".insteadOf [email protected]:
git config --global url."https://".insteadOf git://

Update package.json to use explicit git+https://.