Fragments

GraphQL fragments can be used to give GraphQL queries a structure or extract repeating query sections into reusable parts.

Fragments can be defined only in query payload, using the given syntax:

fragment fragmentName on TypeName {
    field
    otherField
}

fragmentName is the fragment's name (any valid GraphQL field name) and TypeName is the name of the GraphQL type from the schema for which this fragment is used.

To use fragment in a query, place three dots followed by its name (...fragmentName) in a place where its fields should be included:

fragment userProfileFields on User {
    id
    username
    slug
}

query GetUserProfile($id: ID!) {
    user(id: $id) {
        ...userProfileFields
    }
}

In the above example fragment userProfileFields is used to specify a list of fields for the User type in the GetUserProfile query, but outside the query { ... } body itself.

Fragments can also be used in other fragments, and used multiple times within a query:

fragment threadsListUserFields on User {
    id
    username
    slug
}

fragment threadsListThreadFields on Thread {
    id
    title
    slug
    starter {
        ...threadsListUserFields
    }
    poster {
        ...threadsListUserFields
    }
}

query GetCategoryThreads($category: ID!) {
    threads(category: $category) {
        edge {
            node {
                ...threadsListThreadFields
            }
            cursor
        }
        hasMore
    }
}

The threadsListUserFields fragment is used to specify fields for User type to query in User fields of Thread type, itself queried for in the GetCategoryThreads operation.

Fragments can be used in queries, mutations and subscriptions.

While it is not a syntax error to define a GraphQL fragment in schema.graphql, such fragments are discarded from the final GraphQL schema and can't be used in queries.