OnionShare

OnionShare turns your own computer into the server for whatever you want to hand to someone else. It starts a local web service, publishes it as a Tor onion service, and gives you an address to pass on; the other person opens that address in Tor Browser. Nothing is uploaded to a company's storage, and the data travels over the Tor network.

The program has several modes. Share mode sends files or folders, with an option to stop the service by itself once they have been downloaded. Receive mode does the opposite, giving other people an upload page that writes into a folder you choose. Website mode serves a directory of static HTML, CSS and images. Chat mode opens a room that keeps no history on disk.

Because the transfer runs from your machine, both sides have to be online at the same time, and the address stops working the moment you close the program. An address can be handed out as it is, or restricted with a private key that the recipient must enter first.