If you contribute to both personal and professional projects, you’ve likely run into the frustrating situation where Git doesn’t know which identity or SSH key to use. Fortunately, due to the power of ssh and git, with a few config tweaks, you can cleanly separate your personal and work GitHub identities and seamlessly switch between them.

This guide walks through setting up your CLI environment on macOS (or Linux) to:

• Use separate SSH keys for personal and work GitHub accounts
• Automatically route the correct key to the correct GitHub username
• Configure Git to use the appropriate user.name and user.email per project

Step 1: Generate SSH Keys for Each Account

# Personal GitHub key
ssh-keygen -t ed25519 -C "[email protected]" -f ~/.ssh/id_ed25519

# Work GitHub key
ssh-keygen -t ed25519 -C "[email protected]" -f ~/.ssh/id_ed25519_work

Then add them to your macOS keychain:

eval "$(ssh-agent -s)"
ssh-add --apple-use-keychain ~/.ssh/id_ed25519
ssh-add --apple-use-keychain ~/.ssh/id_ed25519_work

Step 2: Add Public Keys to GitHub

Copy the contents of ~/.ssh/id_ed25519.pub and ~/.ssh/id_ed25519_work.pub, and add them to your respective GitHub accounts under Settings > SSH and GPG Keys.

Step 3: Configure Your SSH Client

Edit your ~/.ssh/config to define separate host aliases for GitHub:

# Personal GitHub
Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519
  UseKeychain yes
  AddKeysToAgent yes
  IdentitiesOnly yes

# Work GitHub
Host github.com-work
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_work
  UseKeychain yes
  AddKeysToAgent yes
  IdentitiesOnly yes

The key line here is IdentitiesOnly yes, which ensures SSH only uses the specified identity rather than trying every key in your agent.

Step 4: Configure Git to Rewrite URLs

Git doesn’t know about SSH aliases like github.com-work, so you have to teach it to rewrite URLs.

Add the following to your ~/.gitconfig:

[url "[email protected]:your-work-username/"]
    insteadOf = git@github.com:your-work-username/
    insteadOf = https://github.com/your-work-username/
[url "[email protected]:"]
    insteadOf = https://github.com/

This means:

• URLs for your work account (e.g., [email protected]:your-work-username/repo.git) will be rewritten to use your github.com-work SSH alias.
• Other GitHub URLs will use your personal identity.

Step 5: Set Git User Info Per Project

For your personal projects, the default name/email in ~/.gitconfig will likely suffice:

[user]
    name = Your Name
    email = your-personal-email@example.com

To override Git user info for work projects, add this to ~/.gitconfig:

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

Then create ~/.gitconfig-work with:

[user]
    name = Your Work Name
    email = your-work-email@example.com

This automatically applies your work Git identity to all repos under ~/git/work/.

Bonus: Testing

To test your setup:

# Personal GitHub
ssh -T [email protected]

# Work GitHub
ssh -T [email protected]

Both should return something like:

Hi yourusername! You've successfully authenticated...

And to confirm which key Git is using:

GIT_TRACE=1 GIT_SSH_COMMAND="ssh -v" git fetch

Look for Offering public key: and Authenticated to github.com lines.

Final Thoughts

With this setup, you can:

• Clone work repos as [email protected]:your-work-username/repo.git and they’ll auto-use your work SSH key
• Clone personal repos normally and use your personal key
• Keep your commits clean with the right name/email on every repo

This makes it easy to contribute to both personal and professional projects without messing around with keys, passwords, or constantly switching Git config manually.

Happy coding! ⚡