Uploading and Storing Files
Files can be uploaded by your users and stored in Convex. You can choose to implement this either:
- Via an HTTP action that accepts the file in the request body and stores it directly
- By generating an upload URL to which the client uploads a potentially large file
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 next.
The highlighted lines make the actual request to the HTTP action:
import { FormEvent, useRef, useState } from "react";
const convexSiteUrl = import.meta.env.VITE_CONVEX_SITE_URL;
export default function App() {
const imageInput = useRef<HTMLInputElement>(null);
const [selectedImage, setSelectedImage] = useState<File | null>(null);
async function handleSendImage(event: FormEvent) {
event.preventDefault();
// e.g. https://happy-animal-123.convex.site/sendImage?author=User+123
const sendImageUrl = new URL(`${convexSiteUrl}/sendImage`);
sendImageUrl.searchParams.set("author", "Jack Smith");
await fetch(sendImageUrl, {
method: "POST",
headers: { "Content-Type": selectedImage!.type },
body: selectedImage,
});
setSelectedImage(null);
imageInput.current!.value = "";
}
return (
<form onSubmit={handleSendImage}>
<input
type="file"
accept="image/*"
ref={imageInput}
onChange={(event) => setSelectedImage(event.target.files![0])}
disabled={selectedImage !== null}
/>
<input
type="submit"
value="Send Image"
disabled={selectedImage === null}
/>
</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:
import { httpRouter } from "convex/server";
import { httpAction } from "./_generated/server";
import { api } from "./_generated/api";
const http = httpRouter();
http.route({
path: "/sendImage",
method: "POST",
handler: httpAction(async (ctx, request) => {
// Step 1: Store the file
const blob = await request.blob();
const storageId = await ctx.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 ctx.runMutation(api.messages.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:
- Generate an upload URL using a mutation that calls
storage.generateUploadUrl(). - Send a POST request with the file contents to the upload URL and receive a storage ID.
- 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:
import { FormEvent, useRef, useState } from "react";
import { useMutation } from "convex/react";
import { api } from "../convex/_generated/api";
export default function App() {
const generateUploadUrl = useMutation(api.messages.generateUploadUrl);
const sendImage = useMutation(api.messages.sendImage);
const imageInput = useRef<HTMLInputElement>(null);
const [selectedImage, setSelectedImage] = useState<File | null>(null);
const [name] = useState(() => "User " + Math.floor(Math.random() * 10000));
async function handleSendImage(event: FormEvent) {
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 = "";
}
return (
<form onSubmit={handleSendImage}>
<input
type="file"
accept="image/*"
ref={imageInput}
onChange={(event) => setSelectedImage(event.target.files![0])}
disabled={selectedImage !== null}
/>
<input
type="submit"
value="Send Image"
disabled={selectedImage === null}
/>
</form>
);
}
Generating the upload URL
An upload URL can be generated by the
storage.generateUploadUrl
function of the MutationCtx object:
import { mutation } from "./_generated/server";
export const generateUploadUrl = mutation(async (ctx) => {
return await ctx.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:
import { mutation } from "./_generated/server";
export const sendImage = mutation({
args: { storageId: v.string(), author: v.string() },
handler: async (ctx, args) => {
await ctx.db.insert("messages", {
body: args.storageId,
author: args.author,
format: "image",
});
},
});