CSDEF File

What are CSDEF files and how to open them

Are you having problems opening a CSDEF file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CSDEF files.

What is a CSDEF file?

A .CSDEF file is an Azure Service Definition Schema file.

Azure Service Definition Schema files define how a Microsoft Azure Cloud Service application is structured before deployment. They are written in XML and created when a developer builds a cloud service project using the Azure SDK. They describe what roles the application includes (such as WebRole or WorkerRole), what endpoints those roles expose, what certificates or resources the service needs, what startup tasks to run, and how big each role's virtual machine should be. Once the service is running, the definition file cannot be changed without redeploying.

The definition schema works alongside a configuration file that supplies runtime settings, such as how many instances of each role to run, values of configuration settings, and certificates' details. The definition file gives the fixed blueprint - roles, endpoints, resources - while the configuration file supplies values that can sometimes be updated live. Together with a service package (which bundles code, binaries, and dependencies), these files form the cloud service package Azure uses for deployment.

The schema requires a top-level ServiceDefinition element. Attributes include name (required), schemaVersion, upgradeDomainCount, and topologyChangeDiscovery. Inside this element are zero or more WebRole or WorkerRole elements (up to 25 total), optional elements such as LoadBalancerProbes and NetworkTrafficRules, and definitions for endpoints, configuration settings, certificates, local storage, imports/modules, and startup tasks.

How to open CSDEF files

Important: Different programs may use files with the CSDEF file extension for different purposes, so unless you are sure which format your CSDEF file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: September 19, 2026

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