File Uploads

File Uploads on Nostr

This project includes a useUploadFile hook that uploads files to Blossom servers and returns NIP-94-compatible tags. Use it whenever a feature needs to accept a user-provided file (avatars, banners, post attachments, etc.).

The useUploadFile Hook

import { useUploadFile } from "@/hooks/useUploadFile";

function MyComponent() {
  const { mutateAsync: uploadFile, isPending: isUploading } = useUploadFile();

  const handleUpload = async (file: File) => {
    try {
      // Returns an array of NIP-94-compatible tags.
      // The first tag is the `url` tag; its second element is the file URL.
      const tags = await uploadFile(file);
      const url = tags[0][1];
      // ...use the url
    } catch (error) {
      // ...handle errors (show a toast, etc.)
    }
  };

  // ...rest of component
}

The hook is a TanStack Query mutation, so isPending can drive loading UI and mutateAsync integrates cleanly with async/await flows.

Attaching Files to Events

Kind 0 (profile metadata)

Use the plain URL in the relevant JSON field:

const tags = await uploadFile(file);
const url = tags[0][1];

createEvent({
  kind: 0,
  content: JSON.stringify({ ...existingMetadata, picture: url }),
});

Kind 1 (text notes) and other content events

Append the URL to content, and add one imeta tag per file. imeta carries the NIP-94 metadata (mime type, dimensions, blurhash, etc.) that the uploader returned:

const tags = await uploadFile(file); // e.g. [["url", "https://..."], ["m", "image/png"], ["dim", "1024x768"], ...]
const url = tags[0][1];

// Flatten the NIP-94 tags into a single imeta tag value.
const imeta = tags.map(([name, value]) => `${name} ${value}`);

createEvent({
  kind: 1,
  content: `Check this out ${url}`,
  tags: [["imeta", ...imeta]],
});

Repeat the pattern (one imeta tag per file) for multiple attachments.

Common Patterns

• Avatar / banner pickers: wrap an <input type="file" accept="image/*"> and call uploadFile on change; on success, update the relevant profile field and publish a kind 0 event.
• Post composers: call uploadFile for each selected file before publishing the note, then build imeta tags alongside content.
• Progress UI: use isPending from the mutation to disable the submit button and show a spinner or skeleton.
• Error handling: wrap uploadFile in try/catch and surface failures via useToast — network and Blossom-server errors are common and should never break the UI.

Constraints

• The hook requires a logged-in user (Blossom auth is signed by the user's signer). Guard uploads behind useCurrentUser.
• Don't store or display raw File objects after upload — always use the returned URL.
• Large files may take time; prefer mutateAsync over mutate so the caller can await completion before publishing an event that references the URL.