Working with Files

After your files have been uploaded, you will most likely want to do something with them. This page shows how to work with your uploaded files.

Accessing Files

There are multiple ways to access your files. The most generic way is to construct the URL from the fileKey you get back after the file has been uploaded:

https://utfs.io/f/<FILE_KEY>

This URL will always work for public files and is the default URL returned by the API and from any SDK method. However, sometimes you may want a URL that's scoped to your application, for example when doing image optimizations and want to filter what URLs are allowed to be optimized on your server. For this, the following URL can be used:

https://utfs.io/a/<APP_ID>/<FILE_KEY>

By using this URL pattern, you have more granular control over what URLs are allowed to be optimized. Below is an example of how to setup image optimization allow filtering in Next.js:

/** @type {import('next').NextConfig} */
export default {
  images: {
    remotePatterns: [
      {
        protocol: "https",
        hostname: "utfs.io",
        pathname: "/a/<APP_ID>/*",
      },
    ],
  },
};

Accessing Private Files

If your files are protected with access controls, you will need to request a short-lived presigned URL from the API to access the file. You can request one using UTApi.getSignedUrl, or from the /requestFileAccess API endpoint (see OpenAPI Specification).

Presigned URL follows the same patterns as above, with additional query parameters to authenticate the request.

Other File Operations

Please refer to our server SDK, UTApi for more information on how to work with files. You can also access the API directly using the OpenAPI Specification.