# Hosts for custom test environments
<a name="custom-test-environments-hosts"></a>

 Device Farm supports a set of operating systems with pre-configured software through the use of a test host environment. During test execution, Device Farm utilizes Amazon-managed instances (hosts) that dynamically connect to the selected device under test. This instance is fully cleaned up and not re-used between runs, and is terminated with its generated artifacts after the test run concludes. 

**Topics**
+ [Available test hosts for custom test environments](#custom-test-environments-hosts-available)
+ [Selecting a test host for custom test environments](#test-host-selection)
+ [Supported software within custom test environments](custom-test-environments-hosts-software.md)
+ [Test environment for Android devices](custom-test-environments-hosts-android.md)
+ [Test environment for iOS devices](custom-test-environments-hosts-ios.md)

## Available test hosts for custom test environments
<a name="custom-test-environments-hosts-available"></a>

 The test hosts are fully managed by Device Farm. The following table lists the currently available and supported Device Farm test hosts for custom test environments. 


| Device Platform | Test Host | Operating System | Architecture(s) | Supported Devices | 
| --- | --- | --- | --- | --- | 
|  Android  |  amazon\$1linux\$12  |  Amazon Linux 2  |  x86\$164  |  Android 6 and above  | 
|  iOS  |  macos\$1sequoia  |  macOS Sequoia (version 15)  |  arm64  |  iOS 15 to 26  | 

**Note**  
Periodically, Device Farm adds new test hosts for a device platform to support newer device OS versions and its dependencies. When this occurs, older test hosts for the respective device platform are subject to end of support.

### Operating system version
<a name="test-host-os"></a>

 Each available test host uses a specific version of the operating system supported on Device Farm at the time. Although we try to be on the latest OS version, this may might not be the latest publicly distributed version available. Device Farm will periodically update the operating system with minor version updates and security patches. 

 To know the specific version (including the minor version) of the operating system in use during your test run, you can add the following snippet of code to any of your test spec file's phases. 

**Example**  

```
phases:
  install:
    commands:
      # The following example prints the instance's operating system version details
      - |-
        if [[ "Darwin" == "$(uname)" ]]; then
          echo "$(sw_vers --productName) $(sw_vers --productVersion) ($(sw_vers --buildVersion))";
        else
          echo "$(. /etc/os-release && echo $PRETTY_NAME) ($(uname -r))";
        fi
```

## Selecting a test host for custom test environments
<a name="test-host-selection"></a>

 You can specify the Android and iOS test host in the appropriate `android_test_host` and `ios_test_host` variables of your [test spec file](custom-test-environment-test-spec.md#custom-test-environment-test-spec-syntax). 

 If you do not specify a test host selection for the given device platform, tests will run on the test host that Device Farm has set as the default for the specified device and test configuration. 

**Important**  
When testing on iOS 18 and below, a legacy test host will be used when a host is not selected. For more information, see the topic on the [Legacy iOS test host](custom-test-environments-hosts-ios.md#legacy-ios-host). 

 As an example, review the following code snippet: 

**Example**  

```
version: 0.1
android_test_host: amazon_linux_2
ios_test_host: macos_sequoia

phases:
  # ...
```