The Tor Project has announced plans to stop supporting Tor 0.4.8 and earlier releases on September 1, 2026, as it prepares the network for the deployment of Arti, its Rust-based implementation of Tor.
The announcement concerns the underlying Tor software used by relays, onion services, and applications that integrate with Tor, not the Tor Browser version number most users see. Users running an up-to-date Tor Browser are not expected to be affected, as current browser releases already include supported Tor versions.
Tor 0.4.8 reached end-of-life on June 1, 2026, and will not receive any further updates. While the Tor Project generally avoids breaking compatibility with unsupported releases, it says maintaining support for 0.4.8 would delay network improvements and complicate ongoing development work tied to Arti.
The Tor Project is the nonprofit organization behind the Tor anonymity network, which routes internet traffic through volunteer-operated relays to help protect users' privacy and conceal their online activity. Beyond Tor Browser, the software is also embedded in various privacy tools, services, and self-hosted applications.
The primary reason for the cutoff is the planned removal of obsolete fields from Tor's directory protocol, which distributes relay and network information to clients. In Tor 0.4.9, TAP onion keys and family lines were deprecated, but they have remained in the directory data to maintain compatibility with older software.
According to the Tor Project, removing these fields will reduce the amount of directory data clients download, lowering bandwidth usage and helping Tor instances bootstrap faster, particularly on slower connections.
However, Tor 0.4.8 and earlier releases still expect TAP onion keys to be present. Once the fields are removed, those older versions will no longer be able to process directory information correctly, making them incompatible with the network.
The project also cited Arti development as a factor behind the decision. Arti is a Rust-based reimplementation of Tor that is expected to play an increasingly important role in the network's future. The Tor Network Team said integrating an Arti-based directory authority will be easier if it no longer has to support deprecated protocol fields and other legacy functionality.
The Tor Project has begun contacting downstream projects known to ship older Tor versions and is encouraging community members to help identify software that still relies on unsupported releases. The organization is also tracking outreach efforts to maintainers of affected projects and packages.
Administrators running Tor relays, onion services, or applications that embed Tor should verify which Tor software version they are using and upgrade to the Tor 0.4.9 series or later before September 1, 2026. Organizations that fail to update before the deadline risk losing connectivity to the Tor network once support for the deprecated directory fields is removed.
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