How to use multiple GitHub accounts on Mac?

Like many others, I too have two GitHub accounts, one for personal use and another for work. I was having trouble using both accounts on my mac for personal and office projects. I tried some tutorials and none worked out for me not because they were wrong but the instructions were not comprehensive. In this article I am putting it together all the necessary steps to make it work.

This solution works for macOS Monterey (Version 12.x.x) and later.

Follow the steps below:

1. Generate SSh keys

Assuming you have two different accounts on GitHub: personal@domain.com and work@domain.com. First, generate two different ssh keys for both of your accounts (follow the detailed instructions for generating ssh keys)

ssh-keygen -t ed25519 -C personal@domain.com
ssh-keygen -t ed25519 -C work@domain.com

This will create public/private key pairs for each of these accounts. They should be located in ~/.ssh directory. Assuming generated key files are following

~/.ssh/id_ed25519_personal        # Private key for personal account
~/.ssh/id_ed25519_personal.pub    # Public key for personal account
~/.ssh/id_ed25519_work
~/.ssh/id_ed25519_work.pub

Once the keys are generated run this command

eval "$(ssh-agent -s)"

2. Modify the ~./ssh/config file

You need to modify /.ssh/config file. If it is already there then good else create it by

touch ~/.ssh/config

Open ~/.ssh/config file and modify it as follows

#GitHub for personal
Host github.com                              # Notice the host for personal
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_personal    # Private key for personal account

#Github for work
Host github.com-work                         # Notice the host for work 
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519_work        # Private key for work account

Host *
   # UseKeychain yes                           # If you choose a password to generate keys
   AddKeysToAgent yes                        # Load the keys from keychain into ssh-agent automatically
   IdentitiesOnly yes                        # Tells the ssh-agent server to use the IdentityFiles specified above for each host

Save the file. If you choose to add a password to generate your ssh keys, then uncomment line no. 14 in the above config file.

Do not add any identity file in Host * as suggested here. We are using same host (github.com) for both account. This will make the server to always choose the key for the first added identity to the ssh-agent. Adding IdentitiesOnly yes will prevent the server to make the connection using the first available key and force it to use the respective keys placed under different hosts above.

3. Add keys to macOS Keychain

ssh-add -D           # Will delete all identities added previously from the ssh agent
ssh-add --apple-use-keychain ~/.ssh/id_ed25519_personal
ssh-add --apple-use-keychain ~/.ssh/id_ed25519_work

--apple-use-keychain option will store keys to the keychain and it will make keys persistent boot to boot.

If ssh-add -d is used to remove identities then each keys from keychain will be removed. (Read the man page for ssh-add for more detail).

Check the added keys with ssh-add -l if they are added.

At this point if you reboot your system then keys will be loaded to ssh-agent automatically from the keychain!

4. Add public keys to your corresponding accounts

Do not skip this step!

Add public keys to your account on GitHub. Github already has good documentation for it. For more information, see Adding a new SSH key to your GitHub account.

5. Test the connection

Test the connection for both accounts

ssh -T git@github.com
ssh -T git@github.com-work

If you followed everything to this point, this should return

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

6. Clone the repo

Now is the tricky part.

If you want to use your personal account then copy the remote repo link from GitHub and clone it as

git clone git@github.com:personal/project.git

or reset if you already have cloned

git remote set-url origin git@github.com:personal/project.git

if you want to use your work account then copy the remote repo url from GitHub and modify the url by replacing the host git@github.com by the host git@github.com-work

git clone git@github.com-work:company/project.git

Same rule for setting remote origin url

git remote set-url origin git@github.com-work:company/project.git

7. Test it out

Create a repo on GitHub and then clone it as instructed above. Change the current working directory to the local repository. Configure the user email and name (you can do globally too but I prefer this way) for this repository.
If you cloned the repo for work account then configure it as

git config --local user.email "work@domain.com"
git config --local user.name "work"

Now you can push/pull to/from GitHub remote repository.