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REST API: Population & Field Selection

The REST API by default does not populate any relations, media fields, components, or dynamic zones. Use the populate parameter to populate specific fields and the select parameter to return only specific fields with the query results.

💡 Tip

Strapi takes advantage of the ability of the qs library to parse nested objects to create more complex queries. Use qs directly to generate complex queries instead of creating them manually. Examples in this documentation showcase how you can use qs.

Field selection​

Queries can accept a fields parameter to select only some fields. By default, only the following types of fields are returned:

  • string types: string, text, richtext, enumeration, email, password, and uid,
  • date types: date, time, datetime, and timestamp,
  • number types: integer, biginteger, float, and decimal,
  • generic types: boolean, array, and JSON.

Field selection does not work on relational, media, component, or dynamic zone fields. To populate these fields, use the populate parameter.

Example request: Return only title and body fields

GET /api/users?fields[0]=title&fields[1]=body

Example response
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "title": "test1",
        "body": "Lorem ipsum dolor sit amet, consectetur adipiscing elit."
      }
    }
  ],
  "meta": {
    // ...
  }
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

const qs = require('qs');
const query = qs.stringify(
  {
    fields: ['title', 'body'],
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);

await request(`/api/users?${query}`);
💡 Tip

By default, fields are selected except relations, media, dynamic zones, and components, but you can specify a wildcard * instead of an array.

Population​

Queries can accept a populate parameter to populate various field types:

It is also possible to combine population with multiple operators among various other operators to have much more control over the population.

✏️ Note
  • By default Strapi will not populate any type of fields.
  • It's currently not possible to return just an array of IDs. This is something that is currently under discussion.

Relations & Media fields​

Queries can accept a populate parameter to explicitly define which fields to populate, with the following syntax option examples.

✋ Caution

If the Users & Permissions plugin is installed, the find permission must be enabled for the content-types that are being populated. If a role doesn't have access to a content-type it will not be populated.

Populate 1 level for all relations​

To populate one-level deep for all relations, use the * wildcard in combination with the populate parameter:

Example request

GET /api/articles?populate=*

Example response
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "title": "Test Article",
        "slug": "test-article",
        "body": "Test 1",
        // ...
        "headerImage": {
          "data": {
            "id": 1,
            "attributes": {
              "name": "17520.jpg",
              "alternativeText": "17520.jpg",
              "formats": {
                // ...
              }
              // ...
            }
          }
        },
        "author": {
          // ...
        },
        "categories": {
          // ...
        }
      }
    }
  ],
  "meta": {
    // ...
  }
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

const qs = require('qs');
const query = qs.stringify(
  {
    populate: '*',
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);

await request(`/api/articles?${query}`);

Populate 1 level​

To populate only specific relations one-level deep, use one of the following method:

  • Use the populate parameter as an array and put the relation name inside.
  • Use the populate parameter as an object (using LHS bracket notation) and put the relation name as a key with one of the following values: true, false, t, f, 1, 0.
Example request: populate categories

GET /api/articles?populate[0]=categories

Example response
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "title": "Test Article",
        // ...
        "categories": {
          "data": [
            {
              "id": 1,
              "attributes": {
                "name": "Food"
                // ...
              }
            }
          ]
        }
      }
    }
  ],
  "meta": {
    // ...
  }
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

// Array method
const qs = require('qs');
const query = qs.stringify(
  {
    populate: ['categories'],
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);
await request(`/api/articles?${query}`);
// Object method
const qs = require('qs');
const query = qs.stringify(
  {
    populate: {
      categories: true
    }
  },
  {
    encodeValuesOnly: true // prettify URL
  }
);

await request(`/api/articles?${query}`);

Populate 2 levels​

To populate specific relations, one or several levels deep, use the LHS bracket notation for fields names in combination with the populate parameter.

Example request: populate author and author.company

GET /api/articles?populate[author][populate][0]=company

Example response
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "title": "Test Article",
        // ...
        "author": {
          "data": {
            "id": 1,
            "attributes": {
              "name": "Kai Doe",
              // ...
              "company": {
                "data": {
                  "id": 1,
                  "attributes": {
                    "name": "Strapi"
                    // ...
                  }
                }
              }
            }
          }
        }
      }
    }
  ],
  "meta": {
    // ...
  }
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

const qs = require('qs');
const query = qs.stringify(
  {
    populate: {
      author: {
        populate: ['company'],
      },
    },
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);
await request(`/api/articles?${query}`);
✏️ Note

There is no limit on the number of levels that can be populated. However, the more nested populates there are, the more the request will take time to be performed.

Components & Dynamic Zones​

The populate parameter is used to explicitly define which Dynamic zones, components, and nested components to populate.

Deeply populate a 2-level component & media​

Example request

GET /api/articles?populate[0]=seoData&populate[1]=seoData.sharedImage&populate[2]=seoData.sharedImage.media

Example response
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "title": "Test Article",
        // ...
        "seoData": {
          "id": 1,
          "metaTitle": "Test Article",
          // ...
          "sharedImage": {
            "id": 1,
            "alt": "starSky",
            "media": {
              "data": [
                {
                  "id": 1,
                  "attributes": {
                    "name": "17520.jpg",
                    "formats": {
                      // ...
                    },
                    // ...
                  }
                }
              ]
            }
          }
        }
      }
    }
  ],
  "meta": {
    // ...
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

const qs = require('qs');
const query = qs.stringify(
  {
    populate: [
      'seoData',
      'seoData.sharedImage',
      'seoData.sharedImage.media',
    ],
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);

await request(`/api/articles?${query}`);

Deeply populate a dynamic zone with 2 components​

Dynamic zones are highly dynamic content structures by essence. When populating dynamic zones, you can choose between:

  • a shared population strategy, applying a unique behavior for all the dynamic zone's components
  • or a detailed population strategy, defining per-component populate queries using the on property.
Example request for shared populate strategy

GET /api/articles?populate[testDZ][populate]=*

Example response for shared populate strategy
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "testString": "test1",
        // ...
        "testDZ": [
          {
            "id": 3,
            "__component": "test.test-compo",
            "testString": "test1",
            "testNestedCompo": {
              "id": 3,
              "testNestedString": "testNested1"
                        },
            "otherField": "test"
          },
          {
            "id": 1,
            "__component": "test.test-compo2",
            "testInt": 1,
            "otherField": "test"
          }
        ]
      }
    }
  ],
  "meta": {
    // ...
  }
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

const qs = require('qs');
const query = qs.stringify(
  {
    populate: {
      testDZ: {
        populate: '*',
      },
    },
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);

await request(`/api/articles?${query}`);
Example request for detailed populate strategy

GET /api/articles?populate[testDz][on][test.test-compo][fields][0]=testString&populate[testDz][on][test.test-compo][populate]=*&populate[testDz][on][test.test-compo2][fields][0]=testInt

Example response for detailed populate strategy
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "testString": "test1",
        // ...
        "testDZ": [
          {
            "id": 3,
            "__component": "test.test-compo",
            "testString": "test1",
            "testNestedCompo": {
              "testNestedString": "testNested1"
            }
          },
          {
            "id": 1,
            "__component": "test.test-compo2",
            "testInt": 1
          }
        ]
      }
    }
  ],
  "meta": {
    // ...
  }
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

const qs = require('qs');
const query = qs.stringify(
  {
    populate: {
      testDz: {
        on: {
          'test.test-compo': {
            fields: ['testString'],
            populate: '*',
          },
          'test.test-compo2': {
            fields: ['testInt'],
          },
        },
      },
    },
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);

await request(`/api/articles?${query}`);

Populating createdBy and updatedBy​

The creator fields createdBy and updatedBy are removed from the REST API response by default. The createdBy and updatedBy fields can be returned in the REST API by activating the populateCreatorFields parameter at the content-type level.

To add createdBy and updatedBy to the API response:

  1. Open the content-type schema.json file.

  2. Add "populateCreatorFields": true to the options object:

    "options": {
        "draftAndPublish": true,
        "populateCreatorFields": true
      },

  3. Save the schema.json.

  4. Open the controller [collection-name].js file inside the corresponding API request.

  5. Add the following piece of code, and make sure you replace the [collection-name].js with proper collection name:

    'use strict';
    /**
     *  [collection-name] controller
     */
    const { createCoreController } = require('@strapi/strapi').factories;
    module.exports = createCoreController('api::[collection-name].[collection-name]', ({ strapi }) => ({
      async find(ctx) {
        // Calling the default core action
        const { data, meta } = await super.find(ctx);
        const query = strapi.db.query('api::[collection-name].[collection-name]');
        await Promise.all(
          data.map(async (item, index) => {
            const foundItem = await query.findOne({
              where: {
                id: item.id,
              },
              populate: ['createdBy', 'updatedBy'],
            });
            
            data[index].attributes.createdBy = {
              id: foundItem.createdBy.id,
              firstname: foundItem.createdBy.firstname,
              lastname: foundItem.createdBy.lastname,
            };
            data[index].attributes.updatedBy = {
              id: foundItem.updatedBy.id,
              firstname: foundItem.updatedBy.firstname,
              lastname: foundItem.updatedBy.lastname,
            };
          })
        );
        return { data, meta };
      },
    }));

REST API requests using the populate parameter that include the createdBy or updatedBy fields will now populate these fields.

✏️ Note

The populateCreatorFields property is not available to the GraphQL API.

Combining Population with other operators​

By utilizing the population operator it is possible to combine other operators such as field selection, filters, and sort in the population queries.

✋ Caution

The population and pagination operators cannot be combined.

See the following complex population examples:

Populate with field selection​

Example request

GET /api/articles?fields[0]=title&fields[1]=slug&populate[headerImage][fields][0]=name&populate[headerImage][fields][1]=url

Example response
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "title": "Test Article",
        "slug": "test-article",
        "headerImage": {
          "data": {
            "id": 1,
            "attributes": {
              "name": "17520.jpg",
              "url": "/uploads/17520_73c601c014.jpg"
            }
          }
        }
      }
    }
  ],
  "meta": {
    // ...
  }
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

const qs = require('qs');
const query = qs.stringify(
  {
    fields: ['title', 'slug'],
    populate: {
      headerImage: {
        fields: ['name', 'url'],
      },
    },
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);

await request(`/api/articles?${query}`);

Populate with filtering​

Example request

GET /api/articles?populate[categories][sort][0]=name%3Aasc&populate[categories][filters][name][$eq]=Cars

Example response
{
  "data": [
    {
      "id": 1,
      "attributes": {
        "title": "Test Article",
        // ...
        "categories": {
          "data": [
            {
              "id": 2,
              "attributes": {
                "name": "Cars"
                // ...
              }
            }
          ]
        }
      }
    }
  ],
  "meta": {
    // ...
  }
}

JavaScript query (built with the qs library):

qs can be used to build the query URL used in the example above:

const qs = require('qs');
const query = qs.stringify(
  {
    populate: {
      categories: {
        sort: ['name:asc'],
        filters: {
          name: {
            $eq: 'Cars',
          },
        },
      },
    },
  },
  {
    encodeValuesOnly: true, // prettify URL
  }
);

await request(`/api/articles?${query}`);