File Upload

All Strawberry integrations support multipart uploads as described in the GraphQL multipart request specification. This includes support for uploading single files as well as lists of files.

Uploads can be used in mutations via the Upload scalar. The type passed at runtime depends on the integration:

ASGI / FastAPI / Starlette

Since these integrations use asyncio for communication, the resolver must be async.

Additionally, these servers rely on the python-multipart package, which is not included by Strawberry by default. It can be installed directly, or, for convenience, it is included in extras: strawberry[asgi] (for ASGI/Starlette) or strawberry[fastapi] (for FastAPI). For example:

• if using Pip, pip install 'strawberry[fastapi]'
• if using Poetry, strawberry = { version = "...", extras = ["fastapi"] } in pyproject.toml.

Example:

import typing
import strawberry
from strawberry.file_uploads import Upload


@strawberry.input
class FolderInput:
    files: typing.List[Upload]


@strawberry.type
class Mutation:
    @strawberry.mutation
    async def read_file(self, file: Upload) -> str:
        return await file.read()

    @strawberry.mutation
    async def read_files(self, files: typing.List[Upload]) -> typing.List[str]:
        contents = []
        for file in files:
            content = (await file.read()).decode()
            contents.append(content)
        return contents
 
    @strawberry.mutation
    async def read_folder(self, folder: FolderInput) -> typing.List[str]:
        contents = []
        for file in folder.files:
            content = (await file.read()).decode()
            contents.append(content)
        return contents

Sanic / Flask / Django / AIOHTTP

Example:

import typing
import strawberry
from strawberry.file_uploads import Upload


@strawberry.input
class FolderInput:
    files: typing.List[Upload]


@strawberry.type
class Mutation:
    @strawberry.mutation
    def read_file(self, file: Upload) -> str:
        return file.read().decode()

    @strawberry.mutation
    def read_files(self, files: typing.List[Upload]) -> typing.List[str]:
        contents = []
        for file in files:
            content = file.read().decode()
            contents.append(content)
        return contents
 
    @strawberry.mutation
    def read_folder(self, folder: FolderInput) -> typing.List[str]:
        contents = []
        for file in folder.files:
            contents.append(file.read().decode())
        return contents

Sending file upload requests

The tricky part is sending the HTTP request from the client because it must follow the GraphQL multipart request specifications mentioned above.

The multipart/form-data POST request's data must include:

• operations key for GraphQL request with query and variables
• map key with mapping some multipart-data to exact GraphQL variable
• and other keys for multipart-data which contains binary data of files

Assuming you have your schema up and running, here there are some requests examples:

Sending one file

curl localhost:8000/graphql \
  -F operations='{ "query": "mutation($textFile: Upload!){ readText(textFile: $textFile) }", "variables": { "textFile": null } }' \
  -F map='{ "textFile": ["variables.textFile"] }' \
  -F textFile=@a.txt

Sending a list of files

curl localhost:8000/graphql \
  -F operations='{ "query": "mutation($files: [Upload!]!) { readFiles(files: $files) }", "variables": { "files": [null, null] } }' \
  -F map='{"file1": ["variables.files.0"], "file2": ["variables.files.1"]}' \
  -F file1=@b.txt \
  -F file2=@c.txt

Sending nested files

curl localhost:8000/graphql \
  -F operations='{ "query": "mutation($folder: FolderInput!) { readFolder(folder: $folder) }", "variables": {"folder": {"files": [null, null]}} }' \
  -F map='{"file1": ["variables.folder.files.0"], "file2": ["variables.folder.files.1"]}' \
  -F file1=@b.txt \
  -F file2=@c.txt

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