OnionShare lets you securely and anonymously share a file of any size with someone. It works by starting a web server, making it accessible as a Tor hidden service, and generating an unguessable URL to access and download the file. It doesn't require setting up a server on the Internet somewhere or using a third party filesharing service. You host the file on your own computer and use a Tor hidden service to make it temporarily accessible over the Internet. The other user just needs to use the Tor Browser and to enter the URL to download the file from you.