File Routes

File Routes are the routes you create with the helper instantiated by createUploadthing. Think of them as the "endpoints" for what your users can upload. An object with file routes constructs a file router where the keys (slugs) in the object are the names of your endpoints. You can name your routes whatever you want, preferably something that explains what the route does, e.g. profilePicture, resume, messageAttachment, etc.

Below you can see an example file router with a few routes:

import { createUploadthing, type FileRouter } from "uploadthing/server";

const f = createUploadthing();

export const uploadRouter = {
  // Example "profile picture upload" route - these can be named whatever you want!
  profilePicture: f(["image"])
    .middleware(({ req }) => auth(req))
    .onUploadComplete((data) => console.log("file", data)),

  // This route takes an attached image OR video
  messageAttachment: f(["image", "video"])
    .middleware(({ req }) => auth(req))
    .onUploadComplete((data) => console.log("file", data)),

  // Takes exactly ONE image up to 2MB
  strictImageAttachment: f({
    image: { maxFileSize: "2MB", maxFileCount: 1, minFileCount: 1 },
  })
    .middleware(({ req }) => auth(req))
    .onUploadComplete((data) => console.log("file", data)),

  // Takes up to 4 2mb images and/or 1 256mb video
  mediaPost: f({
    image: { maxFileSize: "2MB", maxFileCount: 4 },
    video: { maxFileSize: "256MB", maxFileCount: 1 },
  })
    .middleware(({ req }) => auth(req))
    .onUploadComplete((data) => console.log("file", data)),

  // Takes up to 4 2mb images, and the client will not resolve
  // the upload until the `onUploadComplete` resolved.
  withAwaitedServerData: f(
    { image: { maxFileSize: "2MB", maxFileCount: 4 } },
    { awaitServerData: true },
  )
    .middleware(({ req }) => auth(req))
    .onUploadComplete((data) => {
      return { foo: "bar" as const };
    }),
} satisfies FileRouter;

export type UploadRouter = typeof uploadRouter;

Route Config

The f function takes two arguments. The first can be an array of FileType, or a record mapping each FileType with a route config. The route config allow more granular control, for example what files can be uploaded and how many of them can be uploaded for a given upload. The array syntax will fallback to applying the defaults to all file types.

A FileType can be any valid web MIME type ↗. For example: use application/json to only allow JSON files to be uploaded.

Additionally, you may pass any of the following custom types: image, video, audio, pdf or text. These are shorthands that allows you to specify the type of file without specifying the exact MIME type. Lastly, there's blob which allows any file type.

A route config can have the following properties:

Route Options

The second argument to the f function is an optional object of route options. Route options are shared configurations for all file types in a route. These configurations are not bound to a specific type of file that is uploaded, but will apply to the entire route.

The f function returns a builder object that allows you to chain methods that will run during the upload process.

import { z } from "zod";

f(["image"])
  .input(z.object({ foo: z.string() }))
  .middleware(async ({ req, input }) => {
    input;
    // ^? { foo: string }
    return {};
  })
  .onUploadError(({ error, fileKey }) => {})
  .onUploadComplete(async (opts) => {});

input

You can pass a Zod ↗ schema to validate user input from the client. This data comes from the client when the upload starts. If validation here fails, an error will be thrown and none of your middleware n'or onUploadComplete functions will be executed.

The input is validated on your server and only leaves your server if you pass it along from the .middleware to the .onUploadComplete. If you only use the input in the middleware without returning it, the Uploadthing server won't have any knowledge of it.

middleware

This is the function where you authorize a user to do an upload. You can also tag the upload with metadata here. Example using Clerk:

import { currentUser } from "@clerk/nextjs";

import { UploadThingError } from "uploadthing/server";

f(["image"])
  .middleware(async ({ req, res }) => {
    const user = await currentUser();

    // Throw if user isn't signed in
    if (!user)
      throw new UploadThingError(
        "You must be logged in to upload a profile picture",
      );

    // Return userId to be used in onUploadComplete
    return { userId: user.id };
  })
  .onUploadComplete(async ({ metadata }) => {
    console.log("Uploaded by user", metadata.userId);
  });

As of v6.4, you can also tag your metadata using the UTFiles symbol to override the uploaded files attributes. This can be used to either rename the file, or set a custom identifer for the file:

import { UTFiles } from "uploadthing/server";

f(["image"])
  .middleware(async ({ req, files }) => {
    const fileOverrides = files.map((file) => {
      const newName = sluggify(file.name);
      const myIdentifier = generateId();
      return { ...file, name: newName, customId: myIdentifier };
    });

    // Return userId to be used in onUploadComplete
    return { foo: "bar" as const, [UTFiles]: fileOverrides };
  })
  .onUploadComplete(async ({ metadata, file }) => {
    // The UTFIles symbol is stripped from the metadata
    metadata; // { foo: "bar" }
    file.customId; // myIdentifier
  });

onUploadError

Called when an error occurs during the upload process.

The function is called with a single object argument with the following properties:

onUploadComplete

This is the function you use to do something with the uploaded file, such as persisting it to your database. Whatever you returned in the middleware will be accessible here. Please note that onUploadComplete is the end of the chain, each route must have one and it must be the last method in the builder chain.

As of v6.0, you can return JSON serializable data from this function, which will be passed to the clientside onClientUploadComplete callback.

The function is called with a single object argument with the following properties: