This is the query that GraphiQL uses (network capture):

query IntrospectionQuery {
  __schema {
    queryType {
      name
    }
    mutationType {
      name
    }
    subscriptionType {
      name
    }
    types {
      ...FullType
    }
    directives {
      name
      description
      locations
      args {
        ...InputValue
      }
    }
  }
}

fragment FullType on __Type {
  kind
  name
  description
  fields(includeDeprecated: true) {
    name
    description
    args {
      ...InputValue
    }
    type {
      ...TypeRef
    }
    isDeprecated
    deprecationReason
  }
  inputFields {
    ...InputValue
  }
  interfaces {
    ...TypeRef
  }
  enumValues(includeDeprecated: true) {
    name
    description
    isDeprecated
    deprecationReason
  }
  possibleTypes {
    ...TypeRef
  }
}

fragment InputValue on __InputValue {
  name
  description
  type {
    ...TypeRef
  }
  defaultValue
}

fragment TypeRef on __Type {
  kind
  name
  ofType {
    kind
    name
    ofType {
      kind
      name
      ofType {
        kind
        name
        ofType {
          kind
          name
          ofType {
            kind
            name
            ofType {
              kind
              name
              ofType {
                kind
                name
              }
            }
          }
        }
      }
    }
  }
}

You can use GraphQL-JS’s introspection query to get everything you’d like to know about the schema:

import { introspectionQuery } from 'graphql';

If you want just the information for types, you can use this:

{
    __schema: {
        types: {
            ...fullType
        }
    }
}

Which uses the following fragment from the introspection query:

fragment FullType on __Type {
    kind
    name
    description
    fields(includeDeprecated: true) {
      name
      description
      args {
        ...InputValue
      }
      type {
        ...TypeRef
      }
      isDeprecated
      deprecationReason
    }
    inputFields {
      ...InputValue
    }
    interfaces {
      ...TypeRef
    }
    enumValues(includeDeprecated: true) {
      name
      description
      isDeprecated
      deprecationReason
    }
    possibleTypes {
      ...TypeRef
    }
  }
  fragment InputValue on __InputValue {
    name
    description
    type { ...TypeRef }
    defaultValue
  }
  fragment TypeRef on __Type {
    kind
    name
    ofType {
      kind
      name
      ofType {
        kind
        name
        ofType {
          kind
          name
          ofType {
            kind
            name
            ofType {
              kind
              name
              ofType {
                kind
                name
                ofType {
                  kind
                  name
                }
              }
            }
          }
        }
      }
    }
  }
`;

If that seems complicated, it’s because fields can be arbitrarility deeply wrapped in nonNulls and Lists, which means that technically even the query above does not reflect the full schema if your fields are wrapped in more than 7 layers (which probably isn’t the case).

You can see the source code for introspectionQuery here.

Using apollo cli:

npx apollo schema:download --endpoint=http://localhost:4000/graphql schema.json

You can use the Hasura’s graphqurl utility

npm install -g graphqurl

gq <endpoint> --introspect > schema.graphql

# or if you want it in json
gq <endpoint> --introspect --format json > schema.json

Full documentation: https://github.com/hasura/graphqurl

Update

After getting sick of modifying my previous script all the time, I caved and made my own CLI tool gql-sdl. I still can’t find a different tool that can download GraphQL SDL with zero config but would love for one to exist.

Basic usage:

$ gql-sdl https://api.github.com/graphql -H "Authorization: Bearer ghp_[redacted]"
directive @requiredCapabilities(requiredCapabilities: [String!]) on OBJECT | SCALAR | ARGUMENT_DEFINITION | INTERFACE | INPUT_OBJECT | FIELD_DEFINITION | ENUM | ENUM_VALUE | UNION | INPUT_FIELD_DEFINITION

"""Autogenerated input type of AbortQueuedMigrations"""
input AbortQueuedMigrationsInput {
  """The ID of the organization that is running the migrations."""
  ownerId: ID!

  """A unique identifier for the client performing the mutation."""
  clientMutationId: String
}
...

The header argument -H is technically optional but most GraphQL APIs require authentication via headers. You can also download the JSON response instead (--json) but that’s a use case already well served by other tools.

Under the hood this still uses the introspection query provided by GraphQL.js, so if you’re looking to incorporate this functionality into your own code see the example below.

Previous answer

Somehow I wasn’t able to get any of the suggested CLI tools to output the schema in GraphQL’s Schema Definition Language (SDL) instead of the introspection result JSON. I ended up throwing together a really quick Node script to make the GraphQL library do it for me:

const fs = require("fs");
const { buildClientSchema, getIntrospectionQuery, printSchema } = require("graphql");
const fetch = require("node-fetch");

async function saveSchema(endpoint, filename) {
    const response = await fetch(endpoint, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ query: getIntrospectionQuery() })
    });
    const graphqlSchemaObj = buildClientSchema((await response.json()).data);
    const sdlString = printSchema(graphqlSchemaObj);
    fs.writeFileSync(filename, sdlString);
}

saveSchema("https://example.com/graphql", "schema.graphql");

getIntrospectionQuery() has the complete introspection query you need to get everything, and then buildClientSchema() and printSchema() turns the JSON mess into GraphQL SDL.

Wouldn’t be too difficult to make this into a CLI tool itself but that feels like overkill.

You can download a remote GraphQL server’s schema with the following command. When the command succeeds, you should see a new file named schema.json in the current working directory.


~$ npx apollo-cli download-schema $GRAPHQL_URL --output schema.json


You can use GraphQL-Codegen with the ast-plugin

npm install --save graphql
npm install --save-dev @graphql-codegen/cli
npx graphql-codegen init

Follow the steps to generate the codegen.yml file

Once the tool is installed, you can use the plugin to download the schema which is schema-ast

The best is to follow the instruction on the page to install itтАж but basically:

npm install --save-dev @graphql-codegen/schema-ast

Then configure the codegen.yml file to set which schema(s) is/are the source of truth and where to put the downloaded schema(s) file:

schema:
  - 'http://localhost:3000/graphql'
generates:
  path/to/file.graphql:
    plugins:
      - schema-ast
    config:
      includeDirectives: true

I was also looking and came across this Medium article on GraphQL

The below query returned many details regarding schema, queries and their input & output params type.

fragment FullType on __Type {
  kind
  name
  fields(includeDeprecated: true) {
    name
    args {
      ...InputValue
    }
    type {
      ...TypeRef
    }
    isDeprecated
    deprecationReason
  }
  inputFields {
    ...InputValue
  }
  interfaces {
    ...TypeRef
  }
  enumValues(includeDeprecated: true) {
    name
    isDeprecated
    deprecationReason
  }
  possibleTypes {
    ...TypeRef
  }
}
fragment InputValue on __InputValue {
  name
  type {
    ...TypeRef
  }
  defaultValue
}
fragment TypeRef on __Type {
  kind
  name
  ofType {
    kind
    name
    ofType {
      kind
      name
      ofType {
        kind
        name
        ofType {
          kind
          name
          ofType {
            kind
            name
            ofType {
              kind
              name
              ofType {
                kind
                name
              }
            }
          }
        }
      }
    }
  }
}
query IntrospectionQuery {
  __schema {
    queryType {
      name
    }
    mutationType {
      name
    }
    types {
      ...FullType
    }
    directives {
      name
      locations
      args {
        ...InputValue
      }
    }
  }
}

You can use IntelliJ plugin JS GraphQL then IDEA will ask you create two files “graphql.config.json” and “graphql.schema.json”

Then you can edit “graphql.config.json” to point to your local or remote GraphQL server:

"schema": {
"README_request" : "To request the schema from a url instead, remove the 'file' JSON property above (and optionally delete the default graphql.schema.json file).",
"request": {
  "url" : "http://localhost:4000",
  "method" : "POST",
  "README_postIntrospectionQuery" : "Whether to POST an introspectionQuery to the url. If the url always returns the schema JSON, set to false and consider using GET",
  "postIntrospectionQuery" : true,
  "README_options" : "See the 'Options' section at https://github.com/then/then-request",
  "options" : {
    "headers": {
      "user-agent" : "JS GraphQL"
    }
  }
}

After that IDEA plugin will auto load schema from GraphQL server and show the schema json in the console like this:

Loaded schema from 'http://localhost:4000': {"data":{"__schema":{"queryType":{"name":"Query"},"mutationType":{"name":"Mutation"},"subscriptionType":null,"types":[{"kind":"OBJECT","name":"Query","description":"","fields":[{"name":"launche

Refer to https://stackoverflow.com/a/42010467/10189759

Would like to point out that if authentications are needed, that you probably cannot just use the config file generated from graphql init

You might have to do something like this, for example, using the github graphql API

{
  "projects": {
    "graphqlProjectTestingGraphql": {
      "schemaPath": "schema.graphql",
      "extensions": {
        "endpoints": {
          "dev": {
            "url": "https://api.github.com/graphql",
            "headers": {
              "Authorization": "Bearer <Your token here>"
            }
          }
        }
      }
    }
  }
}

If you want to do it by your self, read these code:

There is a modular state-of-art tool уАМgraphql-cliуАН, consider looking at it. It uses package уАМgraphqlуАН’s buildClientSchema to build IDL .graphql file from introspection data.

• graphql-cli get-schema :integrated into graphql-cli part 1
• graphql-config EndpointsExtension :integrated into graphql-cli part 2

The graphql npm package’s IntrospectionQuery does

query IntrospectionQuery {
    __schema {
        queryType {
            name
        }
        mutationType {
            name
        }
        subscriptionType {
            name
        }
        types {
            ...FullType
        }
        directives {
            name
            description

            locations
            args {
                ...InputValue
            }
        }
    }
}

fragment FullType on __Type {
    kind
    name
    description

    fields(includeDeprecated: true) {
        name
        description
        args {
            ...InputValue
        }
        type {
            ...TypeRef
        }
        isDeprecated
        deprecationReason
    }
    inputFields {
        ...InputValue
    }
    interfaces {
        ...TypeRef
    }
    enumValues(includeDeprecated: true) {
        name
        description
        isDeprecated
        deprecationReason
    }
    possibleTypes {
        ...TypeRef
    }
}

fragment InputValue on __InputValue {
    name
    description
    type {
        ...TypeRef
    }
    defaultValue
}

fragment TypeRef on __Type {
    kind
    name
    ofType {
        kind
        name
        ofType {
            kind
            name
            ofType {
                kind
                name
                ofType {
                    kind
                    name
                    ofType {
                        kind
                        name
                        ofType {
                            kind
                            name
                            ofType {
                                kind
                                name
                            }
                        }
                    }
                }
            }
        }
    }
}

source

You could use apollo codegen:client. See https://github.com/apollographql/apollo-tooling#apollo-clientcodegen-output