---
type: "fhirpath-function"
title: "FHIRPath Function: replace"
function: "replace"
category: "String Manipulation"
section: "5.6.9"
source: "fhirpath/functions.json"
---
# FHIRPath Function: replace
Returns the input string with all instances of `pattern` replaced with `substitution`. If the substitution is the empty string (`''`), instances of `pattern` are removed from the result. If `pattern` is the empty string (`''`), every character in the input string is surrounded by the substitution, e.g. `'abc'.replace('','x')`{:.fhirpath} becomes `'xaxbxcx'`.

If the input collection, `pattern`, or `substitution` are empty, the result is empty (`{ }`).

If the input collection contains multiple items, the evaluation of the expression will end and signal an error to the calling environment.

``` fhirpath
'abcdefg'.replace('cde', '123') // 'ab123fg'
'abcdefg'.replace('cde', '') // 'abfg'
'abc'.replace('', 'x') // 'xaxbxcx'
```
## Summary
- **Category**: String Manipulation
- **Section**: `5.6.9`
- **Return Type**: `String`
- **Empty Input Result**: `empty`
- **Errors on Multiple Input**: `true`
## Description
Returns the input string with all instances of `pattern` replaced with `substitution`. If the substitution is the empty string (`''`), instances of `pattern` are removed from the result.
## Arguments
- `pattern`: `String` - Pattern to replace
- `substitution`: `String` - Substitution for the pattern
## Type Mapping
- `String-String`
## Example
```fhirpath
'abcdefg'.replace('cde', '123') // 'ab123fg'
'abcdefg'.replace('cde', '') // 'abfg'
'abc'.replace('', 'x') // 'xaxbxcx'
```