OnionShare
Securely and anonymously share files of any size
...With OnionShare, you can share files directly with just an address in Tor Browser.
OnionShare works because it is accessible as a Tor Onion Service. All you need to do is open it and drag and drop the files you want to share into it, and start sharing. It will then generate an unguessable address which the recipient can open in the Tor Browser to download the files; they won't even need their own OnionShare.