Uploading and Storing Files

Files can be uploaded by your users and stored in Convex.

Uploading files via an HTTP action

The most straightforward way of uploading files is by sending the file as a body of an HTTP request.

By defining your own HTTP action to handle such a request you can control who can upload files to your Convex storage. But note that the HTTP action request size is currently limited to 20MB. For larger files you need to use upload URLs as described below.

Example: File Storage with HTTP Actions

Calling the upload HTTP action from a web page

Here's an example of uploading an image via a form submission handler to the sendImage HTTP action defined below:

src/App.jsx

function App() {
  const imageInput = useRef(null);
  const [selectedImage, setSelectedImage] = useState(null);

  async function handleSendImage(event) {
    event.preventDefault();

    // e.g. https://happy-animal-123.convex.site/sendImage?author=User+123
    const sendImageUrl = new URL(`${convexSiteUrl}/sendImage`);
    sendImageUrl.searchParams.set("author", name);

    await fetch(sendImageUrl, {
      method: "POST",
      headers: { "Content-Type": selectedImage.type },
      body: selectedImage,
    });

    setSelectedImage(null);
    imageInput.current.value = "";
  }
…

src/App.jsx

…
  return (
    <form onSubmit={handleSendImage}>
      <input
        type="file"
        accept="image/*"
        ref={imageInput}
        onChange={event => setSelectedImage(event.target.files[0])}
        disabled={selectedImage}
      />
      <input type="submit" value="Send Image" disabled={!selectedImage} />
    </form>
  );

Defining the upload HTTP action

A file sent in the HTTP request body can be stored using the storage.store function of the ActionCtx object. This function returns a storage ID, a globally unique identifier of the stored file.

From the HTTP action you can call a mutation to write the storage ID to a document in your database.

To confirm success back to your hosted website, you will need to set the right CORS headers:

convex/http.js

import { httpRouter } from "convex/server";
import { httpAction } from "./_generated/server";

const http = httpRouter();

http.route({
  path: "/sendImage",
  method: "POST",
  handler: httpAction(async ({ storage, runMutation }, request) => {
    // Step 1: Store the file
    const blob = await request.blob();
    const storageId = await storage.store(blob);

    // Step 2: Save the storage ID to the database via a mutation
    const author = new URL(request.url).searchParams.get("author");
    await runMutation("sendMessage:sendImage", { storageId, author });

    // Step 3: Return a response with the correct CORS headers
    return new Response(null, {
      status: 200,
      // CORS headers
      headers: new Headers({
        // e.g. https://mywebsite.com
        "Access-Control-Allow-Origin": process.env.CLIENT_ORIGIN,
        Vary: "origin",
      }),
    });
  }),
});

Uploading files via upload URLs

Large files can be uploaded directly to your backend using a generated upload URL. This requires the client to make 3 requests:

1. Generate an upload URL using a mutation that calls storage.generateUploadUrl().
2. Send a POST request with the file contents to the upload URL and receive a storage ID.
3. Save the storage ID into your data model via another mutation.

In the first mutation that generates the upload URL you can control who can upload files to your Convex storage.

Example: File Storage with Queries and Mutations

Calling the upload APIs from a web page

Here's an example of uploading an image via a form submission handler to an upload URL generated by a mutation:

src/App.jsx

function App() {
  const generateUploadUrl = useMutation("sendMessage:generateUploadUrl");
  const sendImage = useMutation("sendMessage:sendImage");

  const imageInput = useRef(null);
  const [selectedImage, setSelectedImage] = useState(null);

  async function handleSendImage(event) {
    event.preventDefault();

    // Step 1: Get a short-lived upload URL
    const postUrl = await generateUploadUrl();
    // Step 2: POST the file to the URL
    const result = await fetch(postUrl, {
      method: "POST",
      headers: { "Content-Type": selectedImage.type },
      body: selectedImage,
    });
    const { storageId } = await result.json();
    // Step 3: Save the newly allocated storage id to the database
    await sendImage({ storageId, author: name });

    setSelectedImage(null);
    imageInput.current.value = "";
  }

src/App.jsx

…
  return (
    <form onSubmit={handleSendImage}>
      <input
        type="file"
        accept="image/*"
        ref={imageInput}
        onChange={event => setSelectedImage(event.target.files[0])}
        disabled={selectedImage}
      />
      <input type="submit" value="Send Image" disabled={!selectedImage} />
    </form>
  );

Generating the upload URL

An upload URL can be generated by the storage.generateUploadUrl function of the MutationCtx object:

convex/sendMessage.js

import { mutation } from "./_generated/server";

export const generateUploadUrl = mutation(async ({ storage }) => {
  return await storage.generateUploadUrl();
});

This mutation can control who is allowed to upload files.

The upload URL expires in 1 hour and so should be fetched shortly before the upload is made.

Writing the new storage ID to the database

Since the storage ID is returned to the client it is likely you will want to persist it in the database via another mutation:

convex/sendMessage.js

export const sendImage = mutation(async ({ db }, { storageId, author }) => {
  const message = { body: storageId, author, format: "image" };
  await db.insert("messages", message);
});