How to fix Error response from daemon: unauthorized: authentication required in Docker

The most common fix is to authenticate with the registry before pushing or pulling images.

# Log in to Docker Hub (default registry)
docker login

# You'll be prompted for username and password
# For Docker Hub, use your username (not email) and password or access token

Important: If you use sudo for Docker commands, you must also log in with sudo:

# Credentials are stored separately for root and your user
sudo docker login

After logging in successfully, you should see:

Login Succeeded

Sometimes the default Docker Hub login doesn't work properly. Try specifying the registry URL explicitly:

# Log in with the explicit Docker Hub registry URL
docker login -u your-username https://index.docker.io/v1/

This ensures Docker authenticates with the correct registry endpoint. The index.docker.io/v1/ URL is Docker Hub's official authentication endpoint.

For private registries, use their specific URL:

# AWS ECR
aws ecr get-login-password | docker login --username AWS --password-stdin 123456789.dkr.ecr.region.amazonaws.com

# Azure Container Registry
docker login myregistry.azurecr.io

# Google Container Registry
docker login gcr.io

Docker Hub requires that the image name includes your username or organization as a prefix. If you try to push an image without this prefix, authentication will fail.

# Wrong - image name doesn't include username
docker push myapp:latest
# Error: unauthorized: authentication required

# Correct - tag the image with your username first
docker tag myapp:latest yourusername/myapp:latest
docker push yourusername/myapp:latest

For organizations, use the organization name:

docker tag myapp:latest myorganization/myapp:latest
docker push myorganization/myapp:latest

To check your current Docker Hub username:

cat ~/.docker/config.json | grep -A2 "index.docker.io"

If you're still seeing the error after logging in, your stored credentials may be corrupted or outdated. Clear them and log in fresh:

# Log out from Docker Hub
docker logout

# Log out from a specific registry (if applicable)
docker logout registry.example.com

# Remove the credentials file (backup first)
mv ~/.docker/config.json ~/.docker/config.json.backup

# Log in again
docker login

On macOS and Windows, Docker Desktop stores credentials in the system keychain. You may need to clear those as well:
- macOS: Open Keychain Access, search for "docker", and delete related entries
- Windows: Use Credential Manager to remove Docker-related credentials

Docker Hub recommends using access tokens instead of your account password. Tokens are more secure and can be revoked individually.

1. Go to https://hub.docker.com/settings/security
2. Click "New Access Token"
3. Give it a descriptive name and select permissions
4. Copy the token (you won't see it again)

Use the token to log in:

docker login -u yourusername
# When prompted for password, paste your access token

Or use stdin for automated scripts:

echo "$DOCKER_TOKEN" | docker login -u yourusername --password-stdin

Authentication tokens have expiration timestamps. If your system clock is significantly off, the registry may reject your authentication.

# Check current system time
date

# Compare with actual time
# If off by more than a few minutes, sync the clock

# On Linux with systemd
sudo timedatectl set-ntp true
sudo systemctl restart systemd-timesyncd

# On macOS
sudo sntp -sS time.apple.com

# On Windows (PowerShell as Admin)
w32tm /resync

Docker Desktop on macOS and Windows manages its own clock, which can sometimes drift from the host. Restarting Docker Desktop can help resync the time.

Docker Hub free tier has limitations on private repositories. If you're trying to push a new private image and have reached your limit, you'll see an authentication error.

Check your current usage:
1. Go to https://hub.docker.com/
2. Click on your profile > Account Settings
3. Review your subscription plan and repository limits

Free tier allows:
- Unlimited public repositories
- Limited private repositories (check current limits on Docker Hub)

If you've exceeded limits, you can:
1. Delete unused private repositories
2. Make some repositories public
3. Upgrade to a paid Docker Hub subscription