# AppSpec File structure
<a name="reference-appspec-file-structure"></a>

The following is the high-level structure for an AppSpec file used for deployments to Amazon Lambda and EC2/On-Premises compute platforms.

A value in a YAML-formatted AppSpec file that is a string must not be wrapped in quotation marks ("") unless otherwise specified.

## AppSpec file structure for Amazon ECS deployments
<a name="ecs-appspec-structure"></a>

**Note**  
This AppSpec file is written in YAML, but you can use the same structure to write one in JSON. A string in a JSON-formatted AppSpec file is always wrapped in quotation marks ("").

```
version: 0.0
resources: 
  ecs-service-specifications
hooks: 
  deployment-lifecycle-event-mappings
```

In this structure:

** **version** **  
This section specifies the version of the AppSpec file. Do not change this value. It is required. Currently, the only allowed value is **0.0**. It is reserved by CodeDeploy for future use.  
Specify **version** with a string.

** **resources** **  
This section specifies information about Amazon ECS application to deploy.  
For more information, see [AppSpec 'resources' section for Amazon ECS deployments](reference-appspec-file-structure-resources.md#reference-appspec-file-structure-resources-ecs).

** **hooks** **  
This section specifies Lambda functions to run at specific deployment lifecycle event hooks to validate the deployment.  
For more information, see [List of lifecycle event hooks for an Amazon ECS deployment](reference-appspec-file-structure-hooks.md#reference-appspec-file-structure-hooks-list-ecs).

## AppSpec file structure for Amazon Lambda deployments
<a name="lambda-appspec-structure"></a>

**Note**  
This AppSpec file is written in YAML, but you can use the same structure to write an AppSpec file for a Lambda deployment in JSON. A string in a JSON-formatted AppSpec file is always wrapped in quotation marks ("").

```
version: 0.0
resources: 
  lambda-function-specifications
hooks: 
  deployment-lifecycle-event-mappings
```

In this structure:

** **version** **  
This section specifies the version of the AppSpec file. Do not change this value. It is required. Currently, the only allowed value is **0.0**. It is reserved by CodeDeploy for future use.  
Specify **version** with a string.

** **resources** **  
This section specifies information about the Lambda function to deploy.  
For more information, see [AppSpec 'resources' section (Amazon ECS and Amazon Lambda deployments only)](reference-appspec-file-structure-resources.md).

** **hooks** **  
This section specifies Lambda functions to run at specific deployment lifecycle events to validate the deployment.  
For more information, see [AppSpec 'hooks' section](reference-appspec-file-structure-hooks.md).

## AppSpec file structure for EC2/On-Premises deployments
<a name="server-appspec-structure"></a>

```
version: 0.0
os: operating-system-name
files:
  source-destination-files-mappings
permissions:
  permissions-specifications
hooks:
  deployment-lifecycle-event-mappings
```

In this structure:

** **version** **  
This section specifies the version of the AppSpec file. Do not change this value. It is required. Currently, the only allowed value is **0.0**. It is reserved by CodeDeploy for future use.  
Specify **version** with a string.

** **os** **  
This section specifies the operating system value of the instance to which you deploy. It is required. The following values can be specified:  
+ **linux** – The instance is an Amazon Linux, Ubuntu Server, or RHEL instance.
+ **windows** – The instance is a Windows Server instance.
Specify **os** with a string.

** **files** **  
This section specifies the names of files that should be copied to the instance during the deployment's **Install** event.  
For more information, see [AppSpec 'files' section (EC2/On-Premises deployments only)](reference-appspec-file-structure-files.md).

** **permissions** **  
This section specifies how special permissions, if any, should be applied to the files in the `files` section as they are being copied over to the instance. This section applies to Amazon Linux, Ubuntu Server, and Red Hat Enterprise Linux (RHEL) instances only.  
For more information see, [AppSpec 'permissions' section (EC2/On-Premises deployments only)](reference-appspec-file-structure-permissions.md).

** **hooks** **  
This section specifies scripts to run at specific deployment lifecycle events during the deployment.  
For more information, see [AppSpec 'hooks' section](reference-appspec-file-structure-hooks.md).

**Topics**
+ [AppSpec file structure for Amazon ECS deployments](#ecs-appspec-structure)
+ [AppSpec file structure for Amazon Lambda deployments](#lambda-appspec-structure)
+ [AppSpec file structure for EC2/On-Premises deployments](#server-appspec-structure)
+ [AppSpec 'files' section (EC2/On-Premises deployments only)](reference-appspec-file-structure-files.md)
+ [AppSpec 'resources' section (Amazon ECS and Amazon Lambda deployments only)](reference-appspec-file-structure-resources.md)
+ [AppSpec 'permissions' section (EC2/On-Premises deployments only)](reference-appspec-file-structure-permissions.md)
+ [AppSpec 'hooks' section](reference-appspec-file-structure-hooks.md)