title: Query JSON with JMESPath
description: >-
n8n supports the JMESPath library, to simplify working with JSON formatted
data.
contentType: howto
Query JSON with JMESPath
JMESPath{:target=_blank .external-link} is a query language for JSON that you can use to extract and transform elements from a JSON document. For full details of how to use JMESPath, refer to the JMESPath documentation{:target=_blank .external-link}.
The jmespath() method
n8n provides a custom method, jmespath(). Use this method to perform a search on a JSON object using the JMESPath query language.
The basic syntax is:
=== "JavaScript"
js $jmespath(object, searchString)
=== "Python"
python _jmespath(object, searchString)
To help understand what the method does, here is the equivalent longer JavaScript:
var jmespath = require('jmespath');
jmespath.search(object, searchString);
/// note | Expressions must be single-line The longer code example doesn't work in Expressions, as they must be single-line. ///
object is a JSON object, such as the output of a previous node. searchString is an expression written in the JMESPath query language. The JMESPath Specification{:target=_blank .external-link} provides a list of supported expressions, while their Tutorial and Examples{:target=_blank .external-link} provide interactive examples.
/// warning | Search parameter order
The examples in the JMESPath Specification{:target=_blank .external-link} follow the pattern search(searchString, object). The JMESPath JavaScript library{:target=_blank .external-link}, which n8n uses, supports search(object, searchString) instead. This means that when using examples from the JMESPath documentation, you may need to change the order of the search function parameters.
///
Common tasks
This section provides examples for some common operations. More examples, and detailed guidance, are available in JMESPath's own documentation{:target=_blank .external-link}.
When trying out these examples, you need to set the Code node Mode to Run Once for Each Item.
Apply a JMESPath expression to a collection of elements with projections
From the JMESPath projections documentation{:target=_blank .external-link}:
Projections are one of the key features of JMESPath. Use it to apply an expression to a collection of elements. JMESPath supports five kinds of projections:
- List Projections
- Slice Projections
- Object Projections
- Flatten Projections
- Filter Projections
The following example shows basic usage of list, slice, and object projections. Refer to the JMESPath projections documentation{:target=_blank .external-link} for detailed explanations of each projection type, and more examples.
Given this JSON from a webhook node:
[
{
"headers": {
"host": "n8n.instance.address",
...
},
"params": {},
"query": {},
"body": {
"people": [
{
"first": "James",
"last": "Green"
},
{
"first": "Jacob",
"last": "Jones"
},
{
"first": "Jayden",
"last": "Smith"
}
],
"dogs": {
"Fido": {
"color": "brown",
"age": 7
},
"Spot": {
"color": "black and white",
"age": 5
}
}
}
}
]
Retrieve a list{:target=_blank .external-link} of all the people's first names:
=== "Expressions (JavaScript)"
```js
{{$jmespath($json.body.people, "[*].first" )}}
// Returns ["James", "Jacob", "Jayden"]
```
=== "Code node (JavaScript)"
```js
let firstNames = $jmespath($json.body.people, "[*].first" )
return {firstNames};
/* Returns:
[
{
"firstNames": [
"James",
"Jacob",
"Jayden"
]
}
]
*/
```
=== "Code node (Python)"
python firstNames = _jmespath(_json.body.people, "[*].first" ) return {"firstNames":firstNames} """ Returns: [ { "firstNames": [ "James", "Jacob", "Jayden" ] } ] """
Get a slice{:target=_blank .external-link} of the first names:
=== "Expressions (JavaScript)"
```js
{{$jmespath($json.body.people, "[:2].first")}}
// Returns ["James", "Jacob"]
```
=== "Code node (JavaScript)"
js let firstTwoNames = $jmespath($json.body.people, "[:2].first"); return {firstTwoNames}; /* Returns: [ { "firstNames": [ "James", "Jacob", "Jayden" ] } ] */
=== "Code node (Python)"
python firstTwoNames = _jmespath(_json.body.people, "[:2].first" ) return {"firstTwoNames":firstTwoNames} """ Returns: [ { "firstTwoNames": [ "James", "Jacob" ] } ] """
Get a list of the dogs' ages using object projections{:target=_blank .external-link}:
=== "Expressions (JavaScript)"
```js
{{$jmespath($json.body.dogs, "*.age")}}
// Returns [7,5]
```
=== "Code node (JavaScript)"
js let dogsAges = $jmespath($json.body.dogs, "*.age"); return {dogsAges}; /* Returns: [ { "dogsAges": [ 7, 5 ] } ] */
=== "Code node (Python)"
python dogsAges = _jmespath(_json.body.dogs, "*.age") return {"dogsAges": dogsAges} """ Returns: [ { "dogsAges": [ 7, 5 ] } ] """
Select multiple elements and create a new list or object
Use Multiselect{:target=_blank .external-link} to select elements from a JSON object and combine them into a new list or object.
Given this JSON from a webhook node:
[
{
"headers": {
"host": "n8n.instance.address",
...
},
"params": {},
"query": {},
"body": {
"people": [
{
"first": "James",
"last": "Green"
},
{
"first": "Jacob",
"last": "Jones"
},
{
"first": "Jayden",
"last": "Smith"
}
],
"dogs": {
"Fido": {
"color": "brown",
"age": 7
},
"Spot": {
"color": "black and white",
"age": 5
}
}
}
}
]
Use multiselect list to get the first and last names and create new lists containing both names:
=== "Expressions (JavaScript)"
[[% raw %]]
```js
{{$jmespath($json.body.people, "[].[first, last]")}}
// Returns [["James","Green"],["Jacob","Jones"],["Jayden","Smith"]]
```
[[% endraw %]]
=== "Code node (JavaScript)"
```js
let newList = $jmespath($json.body.people, "[].[first, last]");
return {newList};
/* Returns:
[
{
"newList": [
[
"James",
"Green"
],
[
"Jacob",
"Jones"
],
[
"Jayden",
"Smith"
]
]
}
]
*/
```
=== "Code node (Python)"
python newList = _jmespath(_json.body.people, "[].[first, last]") return {"newList":newList} """ Returns: [ { "newList": [ [ "James", "Green" ], [ "Jacob", "Jones" ], [ "Jayden", "Smith" ] ] } ] """
An alternative to arrow functions in expressions
For example, generate some input data by returning the below code from the Code node:
return[
{
"json": {
"num_categories": "0",
"num_products": "45",
"category_id": 5529735,
"parent_id": 1407340,
"pos_enabled": 1,
"pos_favorite": 0,
"name": "HP",
"description": "",
"image": ""
}
},
{
"json": {
"num_categories": "0",
"num_products": "86",
"category_id": 5529740,
"parent_id": 1407340,
"pos_enabled": 1,
"pos_favorite": 0,
"name": "Lenovo",
"description": "",
"image": ""
}
}
]
You could do a search like "find the item with the name Lenovo and tell me their category ID."
{{ $jmespath($("Code").all(), "[?json.name=='Lenovo'].json.category_id") }}