---
type: "fhirpath-function"
title: "FHIRPath Function: encode"
function: "encode"
category: "Additional String Functions"
section: "5.7.1"
source: "fhirpath/functions.json"
---
# FHIRPath Function: encode
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The encode function takes a singleton string and returns the result of encoding that string in the given format. The format parameter defines the encoding format. Available formats are:
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|hex |The string is encoded using hexadecimal characters (base 16) in lowercase |
|=|=|
|base64 |The string is encoded using standard base64 encoding, using A-Z, a-z, 0-9, +, and /, output padded with = |
|urlbase64 |The string is encoded using url base 64 encoding, using A-Z, a-z, 0-9, -, and _, output padded with = |
|ascii | The string has any character above character code 127 replaced with `?`. *This is a lossy encoding, and not reversible via `decode`*
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Base64 encodings are described in [RFC4648](https://tools.ietf.org/html/rfc4648#section-4).
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If the input is empty, the result is empty.
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If no format is specified, the result is empty.
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## Summary
- **Category**: Additional String Functions
- **Section**: `5.7.1`
- **Return Type**: `String`
- **Empty Input Result**: `empty`
- **Errors on Multiple Input**: `true`
## Description
The encode function takes a singleton string and returns the result of encoding that string in the given format. Available formats are hex, base64, and urlbase64.
## Arguments
- `format`: `String` - Encoding format (hex, base64, urlbase64)
## Type Mapping
- `String-String`
## Example
```fhirpath
'test'.encode('hex') // returns hexadecimal representation
```