How to fix remote: Permission to user/repo.git denied to username. fatal: unable to access in Git

First, determine which account Git is actually authenticating with. The error message itself tells you this:

remote: Permission to user/repo.git denied to OTHER_USERNAME.

This means Git is authenticating as OTHER_USERNAME, not the account you intended. Verify the current authentication:

For SSH:

# Test which account SSH connects with
ssh -T [email protected]

# Expected output:
# Hi YOUR_USERNAME! You've successfully authenticated...

For HTTPS:

# Check stored credentials
git config --global credential.helper

# On Windows, check Credential Manager for stored GitHub credentials
# On macOS, check Keychain Access for github.com entries

If the username shown doesn't match the account that owns the repository, you've identified the problem.

If you're using HTTPS and the wrong credentials are cached, remove them:

On Windows (Credential Manager):
1. Open Control Panel > Credential Manager > Windows Credentials
2. Find entries for git:https://github.com or github.com
3. Click each entry and select Remove

Or via command line:

cmdkey /delete:git:https://github.com
cmdkey /delete:LegacyGeneric:target=git:https://github.com

On macOS (Keychain):

# Remove GitHub credentials from Keychain
git credential-osxkeychain erase
host=github.com
protocol=https
# Press Enter twice (Ctrl+D)

# Or open Keychain Access and search for "github.com"

On Linux:

# If using 'store' helper (plain text file)
rm ~/.git-credentials

# If using cache helper
git credential-cache exit

# If using GNOME Keyring
# Open "Passwords and Keys" app and remove GitHub entries

After clearing credentials, Git will prompt you to authenticate again on the next push.

Force Git to use the correct account by including your username in the remote URL:

# Check current remote URL
git remote -v

# Update remote URL with your username for HTTPS
git remote set-url origin https://[email protected]/owner/repo.git

# Verify the change
git remote -v

When you push, Git will prompt for a password - use your Personal Access Token (not your GitHub password).

Alternative: Switch to SSH

# Change to SSH URL (avoids credential conflicts)
git remote set-url origin [email protected]:owner/repo.git

If you use multiple GitHub accounts with SSH, configure SSH to use different keys for each account:

Step 1: Check your SSH keys

ls -la ~/.ssh/
# Look for key pairs like id_ed25519, id_rsa, work_key, personal_key, etc.

Step 2: Configure SSH for multiple accounts
Edit ~/.ssh/config:

# Personal GitHub account
Host github.com
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_ed25519_personal
    IdentitiesOnly yes

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

Step 3: Update your repository's remote URL

# For work repositories, use the custom host
git remote set-url origin git@github-work:company/repo.git

# For personal repositories
git remote set-url origin [email protected]:username/repo.git

Step 4: Verify SSH is using the correct key

# Test personal account
ssh -T [email protected]

# Test work account
ssh -T git@github-work

If your SSH key is attached as a deploy key to another repository, it can only access that specific repository and may block access to others.

Check if your key is a deploy key:
1. Go to the repository settings where push fails
2. Navigate to Settings > Deploy keys
3. Check if your public key appears there

Solution:
1. Remove the deploy key from the repository
2. Add the key to your personal GitHub account instead:
- Go to [github.com/settings/keys](https://github.com/settings/keys)
- Click New SSH key
- Paste your public key (cat ~/.ssh/id_ed25519.pub)
- Save

Deploy keys are meant for CI/CD systems, not personal development. Your personal SSH key should be added to your GitHub account, not individual repositories.

Ensure you actually have write access to the repository:

For your own repositories:
- Go to the repository on GitHub
- You should see "Settings" tab if you're the owner

For repositories you don't own:
- Ask the repository owner to add you as a collaborator
- Go to repository Settings > Collaborators and teams
- They need to add your GitHub username with "Write" or "Admin" permission

For organization repositories:
- Check your organization membership
- You may need to be added to a team with write access
- Organization owners can check: Organization Settings > People > Your username

If you can't get write access:

# Fork the repository instead
# Then push to your fork

# Change remote to your fork
git remote set-url origin https://github.com/YOUR_USERNAME/repo.git

# After making changes, create a Pull Request to the original repo

Your Personal Access Token might lack the necessary permissions. Create a new one with the correct scopes:

For GitHub:
1. Go to [github.com/settings/tokens](https://github.com/settings/tokens)
2. Click Generate new token > Generate new token (classic)
3. Set a descriptive name and expiration
4. Select scopes:
- repo - Required for pushing to private repositories
- workflow - If you need to update GitHub Actions
- admin:org - If pushing to organization repositories
5. Click Generate token and copy it immediately

For fine-grained tokens (more secure):
1. Go to [github.com/settings/tokens?type=beta](https://github.com/settings/tokens?type=beta)
2. Select the specific repository or repositories
3. Set Repository permissions > Contents to "Read and write"
4. Generate the token

Use the new token:

# Clear old credentials first (see Step 2)
git push origin main
# When prompted, enter your username and paste the new token as password

If the repository belongs to an organization with SAML Single Sign-On enabled, you must authorize your token:

1. Go to [github.com/settings/tokens](https://github.com/settings/tokens)
2. Find your Personal Access Token
3. Click Configure SSO next to the token
4. Click Authorize next to the organization name
5. Complete any SSO authentication prompts

For SSH keys with SSO:
1. Go to [github.com/settings/keys](https://github.com/settings/keys)
2. Find your SSH key
3. Click Configure SSO
4. Click Authorize for each organization

You'll know SSO authorization is needed if:
- You can access personal repositories but not organization ones
- The organization uses enterprise SSO/SAML