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# `Fn::Base64`
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The intrinsic function `Fn::Base64` returns the Base64 representation of the input string. This function is typically used to pass encoded data to Amazon EC2 instances by way of the `UserData` property.

## Declaration
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### JSON
<a name="intrinsic-function-reference-base64-syntax.json"></a>

```
{ "Fn::Base64" : valueToEncode }
```

### YAML
<a name="intrinsic-function-reference-base64-syntax.yaml"></a>

Syntax for the full function name:

```
Fn::Base64: valueToEncode
```

Syntax for the short form:

```
!Base64 valueToEncode
```

**Note**  
If you use the short form and immediately include another function in the `valueToEncode` parameter, use the full function name for at least one of the functions. For example, the following syntax isn't valid:  

```
!Base64 !Sub string
!Base64 !Ref logical_ID
```
Instead, use the full function name for at least one of the functions, as shown in the following examples:  

```
!Base64
  "Fn::Sub": string

Fn::Base64:
  !Sub string
```

## Parameters
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valueToEncode  
The string value you want to convert to Base64.

## Return value:
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The original string, in Base64 representation.

## Examples
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### JSON
<a name="intrinsic-function-reference-base64-example.json"></a>

```
{ "Fn::Base64" : "AWS CloudFormation" }
```

### YAML
<a name="intrinsic-function-reference-base64-example.yaml"></a>

```
Fn::Base64: AWS CloudFormation
```

## Supported functions
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You can use any function that returns a string inside the `Fn::Base64` function.