How to Assess Legacy Apps for Azure Readiness

If you’ve ever looked at one of your legacy applications and thought, “Can this really run in the cloud?”, you’re not alone. For many IT and engineering teams, the hardest part of migrating to Microsoft Azure is figuring out what’s actually ready to move.

Before you start your modernization project, you need a clear picture of your application’s readiness. This assessment helps you identify what can move as-is, what needs work, and what might be better off retired.

Here’s a straightforward framework to help you assess your legacy apps for Azure readiness, and a few tools to make your job easier.

1. Start with Discovery

Every migration starts with visibility. Begin by creating an inventory of all your applications and dependencies: servers, databases, services, APIs, and integrations. Many teams underestimate how much their legacy apps rely on outdated components or shared infrastructure.

Microsoft’s Azure Migrate and the App Modernization Guidance is a great starting point: it automatically discovers servers, databases, and virtual machines across your environment and surfaces compatibility details. You can also use the Microsoft Assessment and Planning Toolkit (MAP) to gather this data agentlessly if you prefer an on-prem scan.

2. Evaluate Technical Compatibility

Once you have your inventory, review the technical fit of each application. Look at runtime versions, OS dependencies, external integrations, and database engines.

For example, older Windows Server apps may need to be upgraded or containerized before moving to Azure. Applications running on legacy .NET Frameworks might require modernization to .NET 6 or .NET 8 for cloud deployment.

If you’re not sure, Microsoft’s Cloud Adoption Framework provides detailed guidance on assessing each workload against Azure services.

3. Assess Performance and Scalability

Legacy applications are often tuned for specific on-prem hardware. In the cloud, performance and scalability look different. Compute is elastic, but inefficient code or chatty databases can drive up costs quickly.

Use your current performance metrics (CPU, memory, I/O) to baseline your workloads. Azure’s Migration Assessment tools can estimate VM sizing and cost models based on this data.

This step helps you right-size your Azure resources and avoid “lift-and-overspend” scenarios.

4. Map Out Security and Compliance

Many legacy apps weren’t built for today’s security expectations. Assess how authentication, data protection, and access controls will translate in Azure.

Check if your app depends on hardcoded credentials, custom authentication, or legacy identity frameworks. Plan to integrate with Azure Active Directory (now Entra ID) or Managed Identities for more secure access management.

5. Prioritize and Plan

After your technical and security assessments, categorize each application using the 6 Rs framework:

• Rehost: Lift and shift with minimal changes
• Replatform: Minor updates to use Azure services
• Refactor: Restructure the app for scalability or modernization
• Rebuild: Rewrite the app using modern frameworks
• Retire: Decommission unused or redundant apps
• Retain: Keep certain apps on-prem for now
• Automated Migration: With GAPVelocity AI, you can use our cost and time effective AI solutions to migrate legacy desktop apps to the web and cloud, and completely primed for Azure.

Start small: pick one or two low-risk applications to pilot your migration. The goal is to validate your approach, not boil the ocean.

6. Leverage Azure Readiness Tools

Microsoft offers several free and enterprise-grade tools to help you assess readiness and plan migrations:

• Azure Migrate – End-to-end discovery, assessment, and migration tooling
• SMART (Strategic Migration Assessment and Readiness Tool) – A guided readiness framework aligned with Microsoft’s Cloud Adoption Framework
• App Modernization Guidance for Azure – Guidance and best practices that help you modernize your applications and data.
• Cloud Adoption Framework for Azure - Guidance for each phase of the cloud project.

7. Turn Insights into a Modernization Roadmap

Your readiness assessment should end with a prioritized roadmap:

• List the apps ready for re-hosting now
• Identify dependencies or blockers for others
• Map required modernization tasks (e.g., code refactors, database upgrades)
• Estimate migration costs and timelines
• Assign business priority and owner

Once you’ve done this, you’ll have a clear path to modernization with less surpises.

Compilation of Resources :

• Azure Migrate Overview – Microsoft Learn
• MAP Toolkit – Microsoft Download Center
• Cloud Adoption Framework
• SMART (Strategic Migration Assessment and Readiness Tool) 
• App Modernization Guidance for Azure 
  
  

Final Thoughts

Assessing your legacy apps for Azure readiness is your foundation for a successful modernization strategy. With the right tools and a clear process, you’ll reduce surprises, control costs, and make your move to Azure far more predictable.

Microsoft provides many great resources for modernization, but if you'd like to see how our modernization team can help you run a readiness assessment or plan your migration path, reach out and send us an email.