OnionShare is an open source tool that lets you securely and anonymously share files, host websites, and chat with friends using the Tor network.
You can download OnionShare for Windows and macOS from the OnionShare website.
For macOS you can also use Homebrew:
brew cask install onionshare
See these instructions to install OnionShare in Linux with Flatpak.
To learn how OnionShare works, what its security properties are, how to use it, and how to contribute to the project, check out https://docs.onionshare.org.