Remove support for BitTorrent download

To Do

  • Remove BitTorrent download option
  • Ask sysadmins to deprecate the BitTorrent service
  • Tell Grésilles we're not using their BitTorrent tracker service anymore
  • Tell sysadmins + accounting that we can stop contributing financially to Grésilles' BitTorrent tracker

Initial discussion

Why would we remove it?

  • It uses SHA-1 (until we do #17983 (closed)), which is a security concern, even if we don't trust downloads using BitTorrent more than those from our mirror pool, and even if we still recommend users to verify their downloads.
  • When we migrate to hybrid or v2 Torrents ( #17983 (closed)), some clients won't be able to download our Torrents anymore. So the current tiny "or download using BitTorrent" text on the installation instructions may not be sufficient anymore: we might want to suggest some BitTorrent clients that will work.
  • Making sure that our torrents work is on the critical path of the release process, and has sometimes delayed releases due to slow downloads from our BitTorrent seed (we did not research why).
  • Our BitTorrent seed is 1 more service sysadmins have to pay attention to and maintain (likely pretty low cost, but it adds up).
  • The BitTorrent tracker we use is 1 more 3rd-party service we contribute to financially (the money is not really a problem here; the communication overhead is).
  • It adds a little bit of complexity for users in our installation instructions.
  • BitTorrent is probably used by more technical people. I'm guessing that these 10% of downloads also overlap a lot with people in the Global North that have more access to technology and good Internet.

Why should we keep it?

  • It's a quite popular option: in March 2025, our Torrents were 11% of total downloads
  • It takes some load away from our mirrors pool, which makes at least some HTTPS downloads faster.
  • It might be less web development work to adapt it to hybrid or v2 vs. removing all these bits. But, it won't be a lot of work anyway. And we don't have to maintain bits that were removed, while we do have to maintain bits that were adapted to hybrid or v2. And some of the work needed to remove these bits has been done already.
  • BitTorrent is kind of better to resume downloads (does it automatically + don't have to keep your browser open). Downloading Tails is quite a lot of data but it's also pretty fast on decent connections these days. I wonder if BitTorrent might still be useful to complete a full download on a worse connection.
Edited by boyska