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Git: Multiple Accounts & SSH Keys via ~/.ssh/config

Use case: Multiple GitHub/Bitbucket/GitLab accounts on one machine - personal and work, or accounts across different services - each using a separate SSH key without touching per-project git config.

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1. Generate SSH Keys (ED25519)

ED25519 is preferred over RSA - faster, smaller keys, and required by some services going forward.

ssh-keygen -t ed25519 -C "[email protected]"  -f "~/.ssh/id_ed25519_github_personal"
ssh-keygen -t ed25519 -C "[email protected]"    -f "~/.ssh/id_ed25519_github_work"
ssh-keygen -t ed25519 -C "[email protected]" -f "~/.ssh/id_ed25519_bitbucket_personal"

macOS tilde bug: If ~ causes issues, use the full path:

ssh-keygen -t ed25519 -C "[email protected]" -f "/Users/username/.ssh/id_ed25519_github_personal"

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2. Add Public Keys to Each Service

Copy each .pub file and paste into the service’s SSH key settings:

cat ~/.ssh/id_ed25519_github_personal.pub   # → github.com/settings/keys
cat ~/.ssh/id_ed25519_github_work.pub       # → github.com/settings/keys (other account)
cat ~/.ssh/id_ed25519_bitbucket_personal.pub # → bitbucket.org/account/settings/ssh-keys/

GitLab: gitlab.com/-/profile/keys

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3. Configure ~/.ssh/config

nano ~/.ssh/config

Scenario A - One account per service

Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_github_personal
  IdentitiesOnly yes

Host bitbucket.org
  HostName bitbucket.org
  User git
  IdentityFile ~/.ssh/id_ed25519_bitbucket_personal
  IdentitiesOnly yes

Clone and push as normal - no extra steps:

git clone [email protected]:username/repo.git

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Scenario B - Multiple accounts on the same service

Use custom Host aliases that map to the same HostName:

Host github-personal
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_github_personal
  IdentitiesOnly yes

Host github-work
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_github_work
  IdentitiesOnly yes

Host bitbucket
  HostName bitbucket.org
  User git
  IdentityFile ~/.ssh/id_ed25519_bitbucket_personal
  IdentitiesOnly yes

Use the alias instead of the real hostname in all git commands:

git clone git@github-personal:username/repo.git
git clone git@github-work:org-name/repo.git
git clone git@bitbucket:workspace/repo.git

For existing repos, update the remote:

git remote set-url origin git@github-work:org-name/repo.git

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4. Verify Connections

ssh -T [email protected]        # Scenario A
ssh -T git@github-personal   # Scenario B
ssh -T git@github-work       # Scenario B
ssh -T [email protected]     # Scenario A
ssh -T git@bitbucket         # Scenario B

Expected output:

Hi username! You've successfully authenticated, but GitHub does not provide shell access.

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Key Config Options Explained

Option	What it does
Host	Alias used in git commands. Can be anything.
HostName	The actual domain to connect to.
User	Always git for GitHub, GitLab, Bitbucket.
IdentityFile	Path to the private key to use.
IdentitiesOnly yes	Prevents SSH from trying other keys. Without this, SSH may fall back to a different key and authenticate as the wrong account.

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Notes

• Per-project git config user.email is still needed if commits must show a specific author email - SSH controls authentication, not commit identity.
• To set commit identity per directory (e.g., all repos under ~/work/), use .gitconfig conditional includes:

  # ~/.gitconfig
  [includeIf "gitdir:~/work/"]
    path = ~/.gitconfig-work
  

  # ~/.gitconfig-work
  [user]
    name = Work Name
    email = [email protected]
  

• Add keys to the SSH agent if prompted for passphrase repeatedly:

  ssh-add ~/.ssh/id_ed25519_github_personal
  ssh-add ~/.ssh/id_ed25519_github_work
  

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