Arti 0.0.3 is released: Configuration, predictive circuits, and more!

by nickm | January 14, 2022

Arti is our ongoing project to create a working embeddable Tor client in Rust. It’s nowhere near ready to replace the main Tor implementation in C, but we believe that it’s the future.

We're working towards our 0.1.0 milestone in early March, where our main current priorities are stabilizing our APIs, and resolving issues that prevent integration. We're planning to do releases every month or so until we get to that milestone.

Please be aware that every release between now and then will probably break backward compatibility.

So, what's new in Arti 0.0.3?

Our biggest API change is that we've completely revamped our configuration system to allow changing configuration values from Rust, while the TorClient instance is running.

In the background, we've also implemented a system for “preemptive circuit construction.” Based on which ports you've used in the recent past, it predicts which circuits you'll likely need in the future, and constructs them in advance to lower your circuit latency.

There are also a bunch of smaller features, bugfixes, and infrastructure improvements; see the changelog for a more complete list.

And what's next?

Between now and March, we're going to be focused on three kinds of improvements:

We'll try to do our next release around the start of February. It might have a new error system, support for bootstrap reporting, easier setup, and more!

Here's how to try it out

We rely on users and volunteers to find problems in our software and suggest directions for its improvement. Although Arti isn't yet ready for production use, it should work fine as a SOCKS proxy (if you're willing to compile from source) and as an embeddable library (if you don't mind a little API instability).

Assuming you've installed Arti (with cargo install arti, or directly from a cloned repository), you can use it to start a simple SOCKS proxy for making connections via Tor with:

$ arti proxy -p 9150

and use more or less as you would use the C Tor implementation!

(It doesn't support onion services yet. If compilation doesn't work, make sure you have development files for libsqlite installed on your platform.)

For more information, check out the README file. (For now, it assumes that you're comfortable building Rust programs from the command line). Our CONTRIBUTING file has more information on installing development tools, and on using Arti inside of Tor Browser. (If you want to try that, please be aware that Arti doesn't support onion services yet.)

When you find bugs, please report them on our bugtracker. You can request an account or report a bug anonymously.

And if this documentation doesn't make sense, please ask questions! The questions you ask today might help improve the documentation tomorrow.

Call for comments—Urgent!

We need feedback on our APIs. Sure, we think we're making them more complete and ergonomic… but it's the users' opinion that matters!

Here are some ideas of how you can help:

  1. You can read over the high-level APIs for the arti-client crate, and look for places where the documentation could be more clear, or where the API is ugly or hard to work with.

  2. Try writing more code with this API: what do you wish you could do with Tor in Rust? Give it a try! Does this API make it possible? Is any part of it harder than necessary? (If you want, maybe clean up your code and contribute it as an example?)


Thanks to everybody who has contributed to this release, including dagon, Daniel Eades, Muhammad Falak R Wani, Neel Chauhan, Trinity Pointard, and Yuan Lyu!

And thanks, of course, to Zcash Open Major Grants (ZOMG) for funding this project!

This is a companion discussion topic for the original entry at

After almost 14 years experiences in using tor and following the news I would say tor had two most important mission in these years.
The first was the decision of porting tor to rust.
The second its the ability of porting rust tor implementation to wasm and js.
Implementing js, wasm modules for tor protocol means we finally get rid of frustrating hacky things to get tor embedded in iOS and other platforms apps. Simply we can have tor in any upcoming OS which has a modern browser without modifying a single line of code [ex Fuchsia OS]. Not only this but also we can have relay hosted on browsers in any platform. Millions of relay volunteers on smartphone market which it can even make tor much more untraceable. Now combine all of these volunteers with upcoming 5G which will bring tor a lot of more bandwidth where we can expect stable 1gbps for every tor user.
Writing all of the advantages of porting tor to wasm is countless and maybe time-consuming for readers. So I stop here but I do want to thanks every single person who had made this decision and I want to tell you all even porting tor to wasm is much more important than the decision of porting to rust because Im pretty sure how HUGE is the area the advantages of tor in wasm!

Im very grateful to you all and wish one day we can embed wasm tor in smart glasses, smart watches and other upcoming 5G IOT devices. I’m not rich but if be alive by that day Ill make 1BTC donation to tor team :).
Good luck

1 Like

Thanks, I was wondering whats the general motive for this port as “we believe that its the future” didnt answer that for me.