What's Actually Happening

You're trying to interact with a remote Git repository (push, fetch, clone, or pull), but your request is rejected because Git cannot authenticate you or you lack the necessary permissions for the operation. The error prevents any data transfer with the remote.

The Error You'll See

For HTTPS URLs:

bash
remote: Permission denied to user/username.
fatal: unable to access 'https://github.com/user/repo.git/': The requested URL returned error: 403

For SSH URLs:

bash
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights and the repository exists.

For organization repositories:

bash
remote: Repository not found.
fatal: repository 'https://github.com/org/repo.git/' not found

Or more generically:

bash
fatal: Authentication failed for 'https://github.com/user/repo.git/'

Why This Happens

Permission denied errors occur when: - SSH key is not added to your GitHub/GitLab/Bitbucket account - SSH key has wrong permissions on the file system - Using HTTPS without a credential helper or with expired credentials - Two-factor authentication is enabled but not handled properly - Repository doesn't exist or you don't have access - Deploy key doesn't have write access - SSH agent isn't running or key isn't added - Using the wrong SSH key for the repository

Step 1: Identify Your Remote URL Type

Check what URL you're using:

bash
git remote -v

Output shows either HTTPS:

bash
origin  https://github.com/user/repo.git (fetch)
origin  https://github.com/user/repo.git (push)

Or SSH:

bash
origin  git@github.com:user/repo.git (fetch)
origin  git@github.com:user/repo.git (push)

Step 2: For SSH - Test Your Connection

Test SSH connectivity to GitHub:

bash
ssh -T git@github.com

For GitLab:

bash
ssh -T git@gitlab.com

For Bitbucket:

bash
ssh -T git@bitbucket.org

Successful output:

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

Step 3: Check SSH Key Permissions

SSH requires specific file permissions:

```bash # Check permissions ls -la ~/.ssh

# Fix permissions chmod 700 ~/.ssh chmod 600 ~/.ssh/id_rsa chmod 644 ~/.ssh/id_rsa.pub ```

Step 4: Ensure SSH Agent is Running

Start the SSH agent and add your key:

```bash # Start agent eval "$(ssh-agent -s)"

# Add your key ssh-add ~/.ssh/id_rsa ```

Verify the key is added:

bash
ssh-add -l

Step 5: Verify SSH Key is Added to Provider

For GitHub, check your keys:

bash
# View your public key
cat ~/.ssh/id_rsa.pub

Go to GitHub.com → Settings → SSH and GPG keys, and verify this key is listed.

For multiple keys, configure SSH to use the right one:

``` # ~/.ssh/config Host github.com HostName github.com User git IdentityFile ~/.ssh/id_rsa_work

Host github-personal HostName github.com User git IdentityFile ~/.ssh/id_rsa_personal ```

Step 6: For HTTPS - Set Up Credentials

Install a credential helper:

```bash # macOS git config --global credential.helper osxkeychain

# Windows git config --global credential.helper manager

# Linux git config --global credential.helper cache ```

For GitHub with 2FA, create a personal access token:

  1. 1.Go to GitHub → Settings → Developer settings → Personal access tokens
  2. 2.Generate new token with repo scope
  3. 3.Use the token as your password when prompted

Step 7: Switch Between HTTPS and SSH

If one method doesn't work, try the other:

Switch to SSH:

bash
git remote set-url origin git@github.com:user/repo.git

Switch to HTTPS:

bash
git remote set-url origin https://github.com/user/repo.git

Step 8: Check Repository Access

Verify the repository exists and you have access:

```bash # List your accessible repositories (GitHub CLI) gh repo list --limit 100

# Or check access via API curl -u username:token https://api.github.com/user/repos ```

Step 9: Check Deploy Key Permissions

If using a deploy key (read-only by default):

bash
# Check if the key has write access
ssh -T git@github.com

Deploy keys show as "read-only" unless given write access during setup.

Step 10: Use the Correct Account

If you have multiple accounts, ensure Git uses the right one:

bash
git config user.name "Correct Name"
git config user.email "correct@email.com"

For per-repository configuration:

bash
git config user.name "Work Name"
git config user.email "work@company.com"

Verify the Fix

Test pushing to the remote:

bash
git push origin main

Or test fetching:

bash
git fetch origin

For SSH, verify with verbose output:

bash
GIT_SSH_COMMAND="ssh -v" git push origin main

Successful output shows:

bash
Enumerating objects: 5, done.
Counting objects: 100% (5/5), done.
...
To github.com:user/repo.git
   abc123..def456  main -> main