Introduction

If you want to share large files securely, then I recommend services like Standard Notes FileSend and FireFox Send because of their built-in end-to-end encryption. Both are free and open-source. The source code Standard Notes FileSend is available here and the source code for Firefox Send is available here.

If you want to share files of unlimited size securely and anonymously, then I recommend using the software OnionShare. It is free and open-source software developed by security professional Micah Lee and over one hundred other contributors. The source code is available on GitHub.

You can use OnionShare to share files of unlimited size directly from your computer to other people's computer. OnionShare sends the files over the Tor network, so they are encrypted multiple times and sent without reliance on any third-party servers or services. Therefore, OnionShare is especially useful when you want to share large files without being tracked online or when you want to circumvent censorship.

In this post, I briefly explain how to configure and use it. Before we start, it is important to know what OnionShare protects against. This is from its security design:

  • Third parties don't have access to files being shared.
  • Network eavesdroppers can't spy on files in transit.
  • Anonymity of sender and recipient are protected by Tor.
  • If an attacker enumerates the onion service, the shared files remain safe.

It is also important to know what it does not protect against:

  • Communicating the OnionShare URL might not be secure.
  • Communicating the OnionShare URL might not be anonymous.

Installation

First, download the OnionShare installer from onionshare.org. If you want to be extra careful, then it is a good idea to verify the signatures. After you do that, run the installer as an administrator and start OnionShare.

OnionShare

Settings

When Sharing, Receiving, and Website modes are off, you can adjust the Settings in the top right corner of the screen. Many custom settings are for advanced users, but here are a few useful settings that can help most users:

  • To allow people to download files without a password (e.g., to share files on social media), visit General settings and check Public mode.
  • To use the same URL every time you share and receive (e.g., to share files with the same people on multiple occasions), visit Onion settings and check Use a persistent address.
  • To allow people to download individual files and to allow multiple people to download your files, visit Sharing settings and uncheck Stop sharing after files have been sent.
OnionShare Settings

Sharing

When you start sharing or receiving files with public mode off, you will receive a URL formatted like this for you to share with the people you want to receive your files: http://onionshare:[email protected] Domains ending in .onion can only be accessed from the Tor browser, so they will need to download and install it.

In the example below, public mode was off and OnionShare generated the http://onionshare:[email protected]mfe5r5uad.onion. To download the file test.txt, one would visit the generated address in a Tor browser and login automatically or visit http://bf27asgaxp4skao5sxbsfu57piqdhggrz2apbyz5xpwpl6pmfe5r5uad.onion and login with onionshare as the username and uncurious-siesta as the password.

OnionShare Example

Receiving

OnionShare can be used as an anonymous 'drop box'. This is useful for journalists who want to allow anyone to send them tips anonymously. Please note that receiving documents can be dangerous, especially if they are from strangers, because they may have viruses and other malware. If you want to take potentially dangerous PDFs, office documents, or images and convert them to safe PDFs, you can use software such as Dangerzone.

Websites

You can also use OnionShare to serve static websites right from your computer. Some useful ways to create static websites include templates from Templated, HTML5UP, or Pixelarity (easier) and static site generators (more challenging; may require code knowledge).

Further Resources

The full documentation for OnionShare is available here.


OnionShare relies on the Tor Project for the Tor network. If you think Tor is useful or valuable, please consider donating. The Tor Project is a 501(c)(3) non-profit organization and donations are tax-deductible.