---
title: Folding fields
slug: '2718'
canonical_url: https://docs.coveo.com/en/2718/
collection: javascript-search-framework
source_format: adoc
---
# Folding fields
The [`FoldingForThread`](https://coveo.github.io/search-ui/classes/foldingforthread.html)/[`Folding`](https://coveo.github.io/search-ui/components/folding.html) components rely on three distinct [fields](https://docs.coveo.com/en/200/) in your [index](https://docs.coveo.com/en/204/).
By default, those fields are:

* `@foldingcollection`

Identifies the folding group each [item](https://docs.coveo.com/en/210/) belongs to (for example, all items belonging to the `ABC` folding group should have `ABC` as their `@foldingcollection` field value).

* `@foldingchild`

Uniquely identifies each item.

* `@foldingparent`

Identifies the parent of each item (for example, all items whose parent has `123` as its `@foldingchild` value should have `123` as their `@foldingparent` value).


> **Note**
>
> Any item whose `@foldingchild` and `@foldingparent` field values are identical is considered to have no parent.

**Example**

Assuming you're using the default folding fields, parent-child relationships could be represented as such in your index:

* Sample one-level parent-child relationship:
 ** Original message   @foldingcollection: "ABC"   @foldingchild: "123"   @foldingparent: "123"
  *** Reply 1   @foldingcollection: "ABC"   @foldingchild: "124"   @foldingparent: "123"
  *** Reply 2   @foldingcollection: "ABC"   @foldingchild: "125"   @foldingparent: "123"


You should typically use the `FoldingForThread` component when dealing only with one-level relationships.
* Sample multi-level parent-child relationship:
 ** Original message   @foldingcollection: "ABC"   @foldingchild: "123"   @foldingparent: "123"
  *** Reply 1   @foldingcollection: "ABC"   @foldingchild: "124"   @foldingparent: "123"
   **** Attachment 1   @foldingcollection: "ABC"   @foldingchild: "127"   @foldingparent: "124"
  *** Reply 2   @foldingcollection: "ABC"   @foldingchild: "125"   @foldingparent: "123"


You should typically use the `Folding` component when you may have to deal with multi-level relationships.

If necessary, you can specify custom folding fields to use instead of the default ones with the following `FoldingForThread`/`Folding` configuration options:

* [`field`](https://coveo.github.io/search-ui/components/folding.html#options.field) to override `@foldingcollection`
* [`child`](https://coveo.github.io/search-ui/components/folding.html#options.child) to override `@foldingchild`
* [`parent`](https://coveo.github.io/search-ui/components/folding.html#options.parent) to override `@foldingparent`


> **Important**
>
> If you specify custom folding fields, remember that in the index, each folding field must:
> 
> * Be of the [String type](https://docs.coveo.com/en/1833#field-type).
> * Have the [**Displayable in Results** option](https://docs.coveo.com/en/1833#search-operator-and-displayable-in-results) enabled.
> 
> Moreover, values in the `child` and `parent` fields may only contain up to 60 alphanumeric characters (for example, assuming you're using the default folding fields, `123abc` is a valid `@foldingchild`/`@foldingparent` value, whereas `123_abc` is not).

> **Notes**
>
> * If you're familiar with the Coveo Search API, it's worth mentioning that:
>  ** The `field` option sets the [`filterField`](https://docs.coveo.com/en/13#operation/searchUsingPost-filterField) query parameter.
>  ** The `child` option sets the [`parentField`](https://docs.coveo.com/en/13#operation/searchUsingPost-parentField) (**not** `childField`) query parameter.
>  ** The `parent` option sets the [`childField`](https://docs.coveo.com/en/13#operation/searchUsingPost-childField) (**not** `parentField`) query parameter.
>  ** The [`range`](https://coveo.github.io/search-ui/components/folding.html#options.range) option sets the [`filterFieldRange`](https://docs.coveo.com/en/13#operation/searchUsingPost-filterFieldRange) query parameter.
> * Before the May 2018 release of the JavaScript Search Framework (see [May 2018 release (v2.4094.8)](https://docs.coveo.com/en/410#may-2018-release-v240948)), the option to use for `child` was [`parent-field`](https://coveo.github.io/search-ui/components/folding.html#options.parentfield), and the option to use for `parent` was [`child-field`](https://coveo.github.io/search-ui/components/folding.html#options.childfield).
> Those options are now deprecated.