As someone who works with both Azure and AWS regularly, I’ve had hands-on experience with both Azure Container Registry (ACR) and AWS Elastic Container Registry (ECR). Recently, while migrating my blog’s deployment pipeline to use ECR, I encountered some interesting differences that are worth sharing.
The Basics
Both services provide secure, private Docker container registries that integrate seamlessly with their respective cloud ecosystems. They’re designed to store, manage, and deploy container images for your applications.
Azure Container Registry (ACR)
- Fully managed Docker registry service
- Integrated with Azure Kubernetes Service (AKS), Azure Container Instances, and other Azure services
- Supports Docker images and OCI artifacts
- Available in multiple tiers: Basic, Standard, Premium
AWS Elastic Container Registry (ECR)
- Fully managed Docker container registry
- Integrated with Amazon ECS, EKS, and AWS Lambda
- Supports Docker images and OCI artifacts
- Single pricing model with pay-as-you-go
OCI artifacts are container-related objects that follow the Open Container Initiative (OCI) specifications. Originally, OCI defined standards for Docker container images, but now it covers a broader range of artifacts—including Helm charts, software bill of materials (SBOMs), and other files—stored in container registries.
Pricing Comparison
This is where things get interesting.
Azure Container Registry
ACR uses a tiered pricing model :
- Basic : £4.23/month + storage (£0.083/GB) + bandwidth
- Standard : £16.93/month + storage (£0.083/GB) + bandwidth
- Premium : £42.32/month + storage (£0.083/GB) + bandwidth + geo-replication
The Premium tier adds features like:
- Geo-replication across Azure regions
- Content trust for image signing
- Private link with private endpoints
- Enhanced throughput
AWS Elastic Container Registry
ECR uses simple pay-as-you-go pricing :
- Storage : $0.10/GB per month (£0.08/GB)
- Data Transfer : Standard AWS data transfer pricing
- No base fee - you only pay for what you use
Authentication & Setup
This is where I hit some friction with ECR.
Azure Container Registry
ACR authentication is straightforward:
# Login using Azure CLI
az acr login --name myregistry
# Or use service principal
docker login myregistry.azurecr.io -u $SP_ID -p $SP_PASSWORD
# In pipelines, it's seamless with Azure DevOps tasks
The Azure DevOps integration is particularly smooth - the Docker@2 task handles authentication automatically when using service connections.
AWS Elastic Container Registry
ECR authentication requires an extra step:
# Get login password and pipe to docker login
aws ecr get-login-password --region eu-north-1 | \
docker login --username AWS --password-stdin \
111111111111.dkr.ecr.eu-north-1.amazonaws.com
In my Azure Pipelines, I had to:
- Install AWS CLI (not included by default)
- Configure AWS credentials as environment variables
- Run the login command manually
- task: CmdLine@2
displayName: "Install AWS CLI"
inputs:
script: |
curl "https://awscli.amazonaws.com/awscli-exe-linux-x86_64.zip" -o "awscliv2.zip"
unzip -q awscliv2.zip
./aws/install --bin-dir ~/.local/bin --install-dir ~/.local/aws-cli
- task: CmdLine@2
displayName: "Login to ECR"
env:
AWS_ACCESS_KEY_ID: $(AWS_ACCESS_KEY_ID)
AWS_SECRET_ACCESS_KEY: $(AWS_SECRET_ACCESS_KEY)
inputs:
script: |
export PATH=$HOME/.local/bin:$PATH
aws ecr get-login-password --region eu-north-1 | \
docker login --username AWS --password-stdin \
111111111111.dkr.ecr.eu-north-1.amazonaws.com
Winner : ACR (simpler authentication, especially in Azure DevOps)
Image Naming & URLs
Azure Container Registry
Clean, predictable naming:
myregistry.azurecr.io/myapp:v1.0.0
myregistry.azurecr.io/namespace/myapp:latest
AWS Elastic Container Registry
Includes your AWS account ID:
111111111111.dkr.ecr.eu-north-1.amazonaws.com/funkysi1701/blog:10.1.1.123-develop
The account ID in the URL may pose a security consideration - it’s visible to anyone who has access to your images or deployment configs. Attackers could use the account ID for targeted phishing, social engineering, or brute-force attacks. If combined with leaked credentials or misconfigured permissions, it makes it easier for someone to identify and target your AWS resources.
Winner : ACR (cleaner URLs)
Features Comparison
| Feature | ACR | ECR |
|---|---|---|
| Image Scanning | ✅ Premium tier | ✅ Included |
| Vulnerability Scanning | ✅ Premium tier | ✅ Basic + Enhanced |
| Geo-Replication | ✅ Premium tier | ❌ Manual setup |
| Webhooks | ✅ All tiers | ✅ Included |
| Image Retention Policies | ✅ All tiers | ✅ Lifecycle policies |
| Private Endpoints | ✅ Premium tier | ✅ VPC endpoints |
| Image Signing | ✅ Content Trust | ✅ AWS Signer |
| Cross-Region Replication | ✅ Premium | ❌ Requires manual setup |
| Import from Docker Hub | ✅ Built-in | ❌ Manual |
Integration with Kubernetes
ACR + AKS
Seamless integration with Azure Kubernetes Service:
# Attach ACR to AKS cluster
az aks update --name myaks --resource-group mygroup --attach-acr myregistry
AKS nodes can pull images without credentials. Magical.
ECR + EKS
Also integrated, but requires IAM roles:
# Attach IAM policy to EKS node role
aws iam attach-role-policy \
--role-name eksNodeRole \
--policy-arn arn:aws:iam::aws:policy/AmazonEC2ContainerRegistryReadOnly
Works well once configured, but requires understanding of AWS IAM.
Winner : Tie (both integrate well with their respective K8s offerings)
Developer Experience
What I Like About ACR
- Simple authentication in Azure DevOps
- Clean, readable image URLs
- Excellent documentation
- Azure Portal UI is intuitive
- Helm chart support is first-class
What I Like About ECR
- No minimum cost - truly pay-per-use
- Built-in vulnerability scanning at all levels
- AWS CLI is powerful and ubiquitous
- Great for multi-cloud strategies
- Excellent API and automation support
Pain Points
ACR :
- Premium tier gets expensive for features that should be standard
- Minimum £4/month even for tiny projects
- Geo-replication requires Premium tier (£42/month)
Geo-replication is important because it allows your container images and artifacts to be stored and accessed in multiple geographic regions.
ECR :
- Authentication is more complex outside AWS
- Account ID in image URL
- Requires AWS CLI installation in non-AWS CI/CD
My Real-World Experience
For my blog’s deployment pipeline, I recently migrated from ACR to ECR primarily for cost reasons. Here’s what I learned:
The Migration
Before (ACR):
- Cost: ~£4.50/month (Basic tier + minimal storage)
- Authentication: Seamless in Azure DevOps
- Image URLs: Clean and simple
After (ECR):
- Cost: £0/month (due to free trial)
- Authentication: Required custom pipeline steps
- Image URLs: Include AWS account ID
Was It Worth It?
For my small personal project, yes - saving money is meaningful. But the setup was more complex than I expected.
For enterprise workloads, I’d still choose ACR Premium if I needed:
- Geo-replication
- Content trust
- Azure-native integration
- Enterprise support
Recommendations
Choose ACR if
✅ You’re heavily invested in Azure ecosystem
✅ You need geo-replication
✅ You want seamless AKS integration
✅ You value simplified authentication
✅ You need Azure-native compliance features
Choose ECR if
✅ You want zero minimum costs
✅ You’re on AWS or multi-cloud
✅ You need built-in vulnerability scanning
✅ You prefer pay-per-use pricing
✅ You’re comfortable with IAM and AWS CLI
Conclusion
Both ACR and ECR are excellent services. Your choice should depend on:
- Your cloud platform - Use the registry that matches your deployment target
- Your budget - ECR wins for small projects, ACR Premium for enterprise features
- Your team’s expertise - Stick with what your team knows
- Your requirements - Need geo-replication? ACR Premium. Need low-cost? ECR.
For my personal projects, I’m happy with ECR’s cost savings. For enterprise work, I still recommend ACR Premium for its advanced features and Azure integration.
What’s your experience with container registries? Let me know in the comments!
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