git 'remote: Support for password authentication was removed on August 13, 2021' / 'fatal: Authentication failed' pushing to GitHub over HTTPS. What do I use instead?

Cause: GitHub stopped accepting account passwords for Git operations over HTTPS on August 13, 2021. Git is still sending (or a credential helper has cached) your old password. Authentication must now use a token or SSH key. Fix (best first): 1. Use Git Credential Manager or the GitHub CLI: run gh auth login and choose HTTPS; gh auth setup-git configures it as the credential helper. GitHub recommends these for command-line access. 2. Or create a personal access token: GitHub Settings > Developer settings > Personal access tokens. Fine-grained tokens are the recommended type: limit them to the needed repositories with the minimum permissions and an expiry date. Then, when Git asks for a password, enter the token (your username is still the username). 3. Clear the stale cached password so Git asks again: remove the old github.com entry from the OS credential store (Windows Credential Manager, macOS Keychain Access, or whatever git config --get credential.helper uses), or run git credential reject with the host. 4. Or switch the remote to SSH: add an SSH key to your account and run git remote set-url origin git@github.com:OWNER/REPO.git. 5. In CI use the built-in GITHUB_TOKEN or a secret; never put a token in the remote URL stored in .git/config or in scripts. Treat tokens like passwords: store them in a credential manager or secrets store, not in plain text files. Verify: git ls-remote origin (or git push) succeeds without the error, and the token appears as recently used in your GitHub token settings. Sources: https://github.blog/changelog/2021-08-12-git-password-authentication-is-shutting-down/ https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/managing-your-personal-access-tokens