Arti 1.5.0 Released

08/09/2025

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Major Milestone for Online Privacy: Arti 1.5.0 Released with Onion Service Access

The ongoing effort to build a next-generation Tor client has reached a critical milestone. A new version of Arti, the official Tor implementation written in the Rust programming language, has been released, introducing one of its most anticipated features yet: the ability to connect to Onion Services.

This update represents a significant leap forward in making the privacy-enhancing power of the Tor network more accessible, secure, and modern. For developers and privacy advocates, this is a development worth watching closely.

A Landmark Achievement: Connecting to Onion Services

The headline feature of this new release is the introduction of client-side support for Onion Services (often called “hidden services”). These are websites and services, identifiable by their .onion addresses, that offer enhanced privacy and censorship resistance by routing traffic entirely within the Tor network.

Key details of this new capability include:

Experimental support for connecting to v3 Onion Services is now available. This allows users and applications using the Arti library to access the vast ecosystem of .onion sites, from secure messaging platforms to independent news sources.
The feature is opt-in by default. To maintain stability and signal its experimental nature, developers and users must explicitly enable Onion Service connectivity in their configuration files. This ensures users are aware they are using a brand-new component.
This lays the groundwork for future development. While this release focuses on connecting to Onion Services, it is a crucial prerequisite for the next major goal: allowing users to host their own Onion Services through Arti.

Refined APIs and Under-the-Hood Enhancements

Beyond this major new feature, the release also includes numerous improvements aimed at enhancing stability, security, and developer experience. These refinements are vital for building a robust foundation for the future of the Tor project.

Notable changes include:

A more intuitive client API. For developers building applications on top of Arti, the main TorClient::bootstrap function has been renamed to TorClient::connect, a more accurate and descriptive name for establishing a connection to the Tor network. Older functions have been deprecated to streamline the library.
Significant internal refactoring. A great deal of work has been done to improve the internal circuit manager, which is responsible for building and managing the pathways through the Tor network. This leads to more robust and reliable connections.
Important bug fixes and dependency updates. The update addresses several bugs, including issues with bridge handling and timeout management, making the client more resilient. It also incorporates the latest security updates from its underlying software dependencies.

Why This Matters: Building a More Secure and Modular Tor

Arti is more than just a rewrite of the original C-based Tor client; it is a fundamental re-imagining of how users and applications interact with the Tor network. By leveraging the memory safety guarantees of the Rust programming language, Arti aims to eliminate entire classes of security vulnerabilities that can affect complex C codebases.

Furthermore, its modular design makes it significantly easier to embed Tor’s privacy features directly into a wide range of applications, from secure chat clients to privacy-focused mobile apps. This release, by adding Onion Service support, moves the project dramatically closer to full feature parity with the existing Tor client, paving the way for its eventual adoption as the primary, officially supported implementation.

What’s Next on the Horizon for Arti?

The development team is already looking ahead to the next set of challenges. The roadmap includes several key objectives:

Stabilizing the Onion Service client API.
Beginning work on Onion Service hosting, which will allow users to run their own services through Arti.
Improving support for bridges and pluggable transports to enhance censorship circumvention.

This latest release is a monumental step forward, bringing the promise of a safer, more modern, and more versatile Tor network closer to reality. It empowers developers with new tools and gives privacy-conscious users a glimpse into the future of online anonymity.

Source: https://blog.torproject.org/arti_1_5_0_released/