Transmission (BitTorrent client)

Transmission is a BitTorrent client which features a variety of user interfaces on top of a cross-platform back-end. Transmission is free software licensed under the terms of the GNU General Public License, with parts under the MIT License.

Transmission allows users to quickly download files from multiple peers on the Internet and to upload their own files. By adding torrent files via the user interface, users can create a queue of files to be downloaded and uploaded. Within the file selection menus, users can customise their downloads at the level of individual files. Transmission also seeds, that is, it will automatically share downloaded content.

Transmission allows the assigning of priorities to torrents and to files within torrents, thus potentially influencing which files download first. It supports the Magnet URI scheme and encrypted connections. It allows torrent-file creation and peer exchange compatible with Vuze and μTorrent. It includes a built-in web server so that users can control Transmission remotely via the web. It also supports automatic port-mapping using UPnP/NAT-PMP, peer caching, blocklists for bad peers, bandwidth limits dependent on time-of-day, globally or per-torrent, and has partial support for IPv6. It allows the use of multiple trackers simultaneously, Local Peer Discovery, Micro Transport Protocol (μTP), and UDP tracker. It does not support directly subscribing to RSS feeds containing torrent files for automatic download, but third-party add-ons can supply this functionality.

macOS-specific features include Dock and Growl notifications, automatic updates using Sparkle and Universal Binary (up until version 2.22).

Transmission 4.0.0, released in February 2023, added support for hybrid torrents so that it can work with v1 and hybrid (v1/v2) torrents.

Transmission 1.60 and later removed support for Mac OS X v10.4. Currently, Transmission 1.54 is the last version that runs on Mac OS X 10.4. Although it is possible to compile later versions from source, either by downloading from the project's website or using a package manager like Fink or MacPorts, it is unsupported and any bugs specific to 10.4 will not be fixed. Starting with Transmission 2.30 an Apple Mac with an Intel CPU is needed; PowerPC-based systems are no longer supported natively. Since Transmission 4.0, Apple Silicon is supported as well.

The Transmission back-end (libTransmission) also serves as the basis of the Transmission daemon. The daemon supports a web front-end called Clutch. Older versions have been ported to form the basis of the update system for the video game Metal Gear Online on PlayStation 3, as well as the backend for ImageShack's BitTorrent service.

A portable version is available on PortableApps.com.