> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fga.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Relationship Queries: Check, Read, Expand, ListObjects and ListUsers

> An overview of how to use the Check, Read, Expand, ListObjects and ListUsers APIs

In this guide you will learn the uses of and limitations for the Check, Read, Expand, ListObjects and ListUsers API endpoints.

## Before you start

In order to understand this guide correctly you must be familiar with some [Auth0 FGA Concepts](https://docs.fga.dev/fga-concepts.md) and know how to develop the things that we will list below.

<details>
  <summary>
    Assume that you have the following [authorization model](https://docs.fga.dev/fga-concepts.md#what-is-an-authorization-model).\\

    You have a [type](https://docs.fga.dev/fga-concepts.md#what-is-a-type) called `document` that can have a `reader`
    and `writer`. All writers are readers. `bob` has a `writer` relationship with `document:planning`.
  </summary>

  ```json theme={null}
  [
    // Bob has writer relationship with planning document
    {
      "user": "user:bob",
      "relation": "writer",
      "object": "document:planning"
    }
  ]
  ```

  ***

  In addition, you will need to know the following:

  ### Direct access

  You need to know how to create an authorization model and create a relationship tuple to grant a user access to an object. [Learn more →](https://docs.fga.dev/modeling/basics/modeling-basics.md)

  ### Auth0 FGA concepts

  * A [Type](https://docs.fga.dev/fga-concepts.md#what-is-a-type): a class of objects that have similar characteristics
  * A [User](https://docs.fga.dev/fga-concepts.md#what-is-a-user): an entity in the system that can be related to an object
  * A [Relation](https://docs.fga.dev/fga-concepts.md#what-is-a-relation): is a string defined in the type definition of an authorization model that defines the possibility of a relationship between an object of the same type as the type definition and a user in the system
  * An [Object](https://docs.fga.dev/fga-concepts.md#what-is-an-object): represents an entity in the system. Users' relationships to it can be define through relationship tuples and the authorization model
  * A [Relationship Tuple](https://docs.fga.dev/fga-concepts.md#what-is-a-relationship-tuple): a grouping consisting of a user, a relation and an object stored in Auth0 FGA
</details>

## Check

### What is it for?

The [Check API](https://docs.fga.dev/api/service/relationship-queries/check.md) is an API endpoint that returns whether the user has a certain relationship with an object. Auth0 FGA will resolve all prerequisite relationships to establish whether a relationship exists.

### When to use?

Check can be called if you need to establish whether a particular user has a specific relationship with a particular object.

For example, you can call check to determine whether `bob` has a `reader` relationship with `document:planning`.

The Auth0 FGA API will return `true` because there is an implied relationship as

* every `writer` is also a `reader`
* `bob` is a `writer` for `document:planning`

### Limits

Check out the request rate limits for your [plan](https://docs.fga.dev/subscription-plans.md).

### Caveats and when not to use it

Check is designed to answer the question "Does user:X have relationship Y with object:Z?". It is *not* designed to answer the following questions:

* "Who has relationship Y with object:Z?"
* "What are the objects that userX has relationship Y with?"
* "Why does user:X have relationship Y with object:Z?"

## Batch Check

### What is it for?

The [Batch Check API](https://docs.fga.dev/api/service/relationship-queries/batch-check.md) is an API endpoint that allows you to check multiple user-object-relationship combinations in a single request.

### When to use?

Batching authorization checks together in a single request significantly reduces overall network latency.

Two scenarios are common to use Batch Check:

1. When determining if the user has access to a list of objects (such as [Option 1 in Search with Permissions](https://docs.fga.dev/integration/advanced/search-with-permissions.md#option-1-search-then-check)), filter and sort on your database, then call `/batch-check`. Repeat to perform pagination.
2. When determining fields on a web page the user has access to, call `/batch-check` for every relation necessary to show/hide each field.

For example, you can call Batch Check to determine whether `bob` has `can_view_name`, `can_view_dob`, and `can_view_ssn` relationships with `patient_record:1`.

The Auth0 FGA API will return `true` depending on the level of access assigned to that user and the implied relationships inherited in the authorization model.

### Caveats and when not to use it

If you are making less than 10 checks, it may be faster to call the [Check API](https://docs.fga.dev/api/service/relationship-queries/check.md) in parallel instead of Batch Check.

## Read

### What Is It For?

The [Read API](https://docs.fga.dev/api/service/relationship-tuples/read.md) is an API endpoint that returns the relationship tuples that are stored in the system that satisfy a query.

### When to use?

Read can be called if you need to get all the stored relationship tuples that relate:

1. [**user + relation + object**](#1-read-a-tuple-related-to-a-particular-user-relation-and-object)
2. [**user + relation + object type**](#2-read-all-tuples-related-to-a-particular-user-relation-and-object-type)
3. [**user + object** with any relation](#3-read-all-tuples-related-to-a-particular-user-and-object-with-any-relation)
4. [**user + object type** with any relation](#4-read-all-tuples-related-to-a-particular-user-and-object-type-with-any-relation)
5. [**relation + object** for any user](#5-read-all-tuples-related-to-a-particular-relation-and-object-for-any-user)
6. [**object** with any user and relation](#6-read-all-tuples-related-to-a-particular-object-with-any-user-or-relation)
7. [**all** with any user, relation, or object](#7-read-all-tuples-for-any-user-relation-or-object)

#### 1. Read a tuple related to a particular user, relation, and object

For example, to query if `bob` has a `writer` relationship on `document:planning` (essentially finding out if a tuple exists), one can ask

#### 2. Read all tuples related to a particular user, relation, and object type

For example, to query all the stored relationship tuples `bob` has a `writer` relationship with on type `document:`, one can ask

#### 3. Read all tuples related to a particular user and object with any relation

For example, to query all the stored relationship tuples `bob` has on type `document:planning`, one can ask

#### 4. Read all tuples related to a particular user and object type with any relation

For example, to query all the stored relationship tuples `bob` has on object type `document:`, one can ask

#### 5. Read all tuples related to a particular relation and object for any user

For example, to query all the stored relationship tuples which have the `writer` relation on object `document:planning`, one can ask

#### 6. Read all tuples related to a particular object with any user or relation

For example, to query all the stored relationship tuples for object `document:planning`, one can ask

#### 7. Read all tuples for any user, relation, or object

For example, to query all stored relationship tuples, one can ask

### Limits

Check out the request rate limits for your [plan](https://docs.fga.dev/subscription-plans.md).

### Caveats and when not to use it

The Read API will only return all the stored relationships that match the query specification.
It does not expand or traverse the graph by taking the authorization model into account.

For example, if you specify that `writers` are `viewers` in the authorization model, the Read API will ignore that and it will return tuples where a user is a `viewer` if and only if the `(user_id, "viewer", object_type:object_id)` relationship tuple exists in the system.

In the following case, although all `writers` have reader `relationships` for document objects and `bob` is a `writer` for `document:planning`, if you query for all objects that `bob` has `reader` relationships, it will not return `document:planning`.

> [!NOTE]
>
> Although bob is a writer to document:planning and every writer is also a reader, the Read API will return an empty list because there are no stored relationship tuples that relate bob to document:planning as reader.

## Expand

### What is it for?

The [Expand API](https://docs.fga.dev/api/service/relationship-queries/expand.md) returns all users (including users and usersets) that have a specific relationship with an object.
The response is represented as a tree of users or usersets. To build the full graph of access, you would need to recursively call expand on the leaves returned from the previous expand call.

### When to use?

Expand is used for debugging and to understand why a user has a particular relationship with a specific object.

For example, to understand why `bob` can have a `reader` relationship with `document:planning`, one could first call

The result of this call will be like

```json theme={null}
{
  "tree":{
    "root":{
      "type":"document:planning#reader",
        "leaf":{
          "computed":{
            "userset":"document:planning#writer"
          }
        }
      }
    }
  }
}
```

The returned tree will contain `writer`, for which we will call

The result of this call will be like

```json theme={null}
{
  "tree":{
    "root":{
      "type":"document:planning#writer",
        "leaf":{
          "users":{
            "users":[
              "user:bob"
            ]
          }
        }
      }
    }
  }
}
```

From there, we will learn that

* those related to `document:planning` as `reader` are all those who are related to that document as `writer`
* `bob` is related to `document:planning` as `writer`

### Limits

Check out the request rate limits for your [plan](https://docs.fga.dev/subscription-plans.md).

## ListObjects

### What is it for?

The [ListObjects API](https://docs.fga.dev/api/service/relationship-queries/list-objects.md) is an API endpoint that returns the list of all the objects of a particular type that a specific user has a specific relationship with.

It provides a solution to the [Search with Permissions (Option 3)](https://docs.fga.dev/integration/advanced/search-with-permissions.md#option-3-use-fga-permissions-index) use case for access-aware filtering on small object collections.

### When to use?

Use the ListObjects API to get what objects a user can see based on the relationships they have. See [Search with Permissions](https://docs.fga.dev/integration/advanced/search-with-permissions.md) for more guidance.

There's two variations of the List Objects API.

* The [standard version](https://docs.fga.dev/api/service/relationship-queries/list-objects.md), which waits until all results are ready and sends them in one response.
* The [streaming version](https://docs.fga.dev/api/service/relationship-queries/streamed-list-objects.md), which should be used if you want the individual results as soon as they become available.

### Limits

Check out the request rate limits for your [plan](https://docs.fga.dev/subscription-plans.md).

### Caveats

ListObjects will return the results found within the time allotted (`3s`).

## ListUsers

### What is it for?

The [ListUsers API](https://docs.fga.dev/api/service/relationship-queries/list-users.md) is an API endpoint that that returns all users of a given type that have a specified relationship with an object.

### When to use?

Use the ListUsers API to get which users have a relation to a specific object.

### Caveats

ListUsers will return the results found within the time allotted (`3s`).

## Summary

| | Check | Read | Expand | ListObjects | ListUsers |
| - | - | - | - | - | - |
| Purpose | Check if user has particular relationship with certain object | Return all stored relationship tuples that match query | Expand the specific relationship on a particular object | List all objects of a particular type that a user has a specific relationship with | List all users of a particular type that have a relation to a specific object |
| When to use | Validate if user X can perform Y on object Z | List stored relationships in system | Understand why user X can perform Y on object Z | Filter the objects a user has access to | List the users that have access to an object |

## Related Sections

Check out this additional content for more information on how to query relationships.

[Check API Reference
Official reference guide for the Check API](https://docs.fga.dev/api/service/relationship-queries/check.md)

[Read API Reference
Official reference guide for the Read API](https://docs.fga.dev/api/service/relationship-tuples/read.md)

[Expand API Reference
Official reference guide for the Expand API](https://docs.fga.dev/api/service/relationship-queries/expand.md)

[ListObjects API Reference
Official reference guide for the ListObjects API](https://docs.fga.dev/api/service/relationship-queries/list-objects.md)

[ListUsers API Reference
Official reference guide for the ListUsers API](https://docs.fga.dev/api/service/relationship-queries/list-users.md)