About the Tor Specifications documents

The canonical, official, versions of these documents are on the Tor Specifications website maintained by the Tor Project.

Only the Tor Specifications themselves are approved. The Proposals are, by their nature, drafts.

When linking to the Specifications, consider using one of the links advertised in the Table of Permalinks.

Source code

The Specifications and Proposals are maintained by the Tor Project in a gitlab repository.

Corrections and clarifications are welcome. To propose a change to the Tor protocol, use the Proposals process


The documents are in Markdown and formatted with mdbook. To build the formatted HTML:

cargo install mdbook
git clone https://gitlab.torproject.org/tpo/core/torspec/
cd torspec

The output is then in html/.

Source code structure, and output webtree

There are two mdbook books here:

  • The Tor Specifications: source code in specs/, formatted output in html/.

  • Proposals: source code in proposals/, formatted output in html/proposals/.

Each book's source files are listed, and the chapter defined, in its SUMMARY.md. The format is pretty restrictive; see the mdbook documentation.

Editing advice

To edit these specs, clone the git repository and edit the appropriate file in the spec directory. These files will match the URLs of their corresponding pages, so if you want to edit tor-spec/flow-control.html, you'll be looking for a file called spec/tor-spec/flow-control.md.

We have started a style guide for writing new parts of this spec; as of 2023 it is quite preliminary. You should feel free to edit it!