# Environment variables in Sitecore configs


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I just recently found out that Sitecore have been supporting using **Windows environment variables** in config files since Sitecore 8.2 rev. 160729 (Initial).
 
I was digging around in Sitecore, looking at the `ConfigReader` for [another personal project](https://github.com/Krusen/Additio.Sitecore.DependencyConfigReader "Sitecore Dependency Config Reader") I was working on, when I noticed these lines:

```csharp
// ...

reader.ExpandIncludeFiles(ConfigReader.config.DocumentElement, new Hashtable());
reader.LoadAutoIncludeFiles(ConfigReader.config.DocumentElement);
reader.ReplaceGlobalVariables(ConfigReader.config.DocumentElement);
reader.ReplaceEnvironmentVariables(ConfigReader.config.DocumentElement);

// ...
```
 
Especially the last line - **ReplaceEnvironmentVariables**.
 
As mentioned, this feature was introduced in the intial release of Sitecore 8.2, so actually quite a while ago.
 
To use environment variables in your config files just write it like `$(env:YOUR_CUSTOM_VARIABLE)`. This is pretty much like how global variables are used, e.g. `$(dataFolder)`.
 
For example `$(env:COMPUTERNAME)` would be replaced with the local computer name.
 
This is quite a neat feature that can be very useful, for example in scenarios like multi-server setups where you might want to use machine-specific settings and the like.
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