Even though BitTorrent is a decentralized protocol, it was originally conceived with a centralized component — trackers.
Torrent trackers are responsible for keeping ‘track’ of all peers sharing a specific torrent file. This makes it easy for peers to discover each other and start downloading the torrent quickly.
More recently, trackers are becoming redundant and in some cases can be replaced entirely by ‘trackerless’ technologies like DHT, where the list of peers is actually hosted by torrent peers, rather than a centralized server.
What is a Tracker?
A torrent tracker is simply a server that ‘tracks’ various torrent swarms. The tracker is responsible for maintaining an up-to-date list of peers and seeders sharing each file.
Peers typically ‘announce’ their status to the tracker at set intervals, which allows the tracker to refresh its database.
Many trackers also have a corresponding website, offering an interface for torrent downloads. There’s often a community component as well, such as a voting system or torrent-level commenting (which is useful for identifying incomplete, mislabled or malicious files).
For example, popular public torrent sites like The Pirate Bay are actually trackers with added functionality (the website) on top.
Public vs Private Trackers?
Most users are familiar with public trackers, those accessible without a registration or an invitation.
There are hundreds of public trackers, which are available to anyone with a bittorrent client.
But there are also dozens of private trackers as well. These are private invite-only communities serving hardcore torrenters. Private trackers typically have curated, high-quality content organized around a specific theme or media type (e.g. live audio).
However such trackers are hard to get into and have strict contribution and seeding requirements to maintain your membership.
Are Trackers still necessary?
These days, http trackers are mostly unnecessary, though they can be helpful under certain conditions.
For the most part, tracker functionality can be replaced by magnet links and Distributed Hash Tables (DHT) as long as your network firewall doesn’t block DHT packets. This can be an issue with some VPNs or proxy configurations.
Trackers are still useful for new torrents
If you’re creating new torrents, you’ll still want to announce them to old-school trackers. That’s because DHT can’t replace the torrent-discovery and searchability of public trackers.
If trackers don’t know about your new torrent, nobody will actually be able to find it. So make sure you add a few of the top torrent trackers to your announce list when publishing brand new torrent.
Trackers Privacy (what they know about you)
Trackers are basically large databases of bittorrent metadata, and they can store a fair amount of sensitive information.
For example, trackers know:
- your public IP address
- all swarms / files you’re currently sharing
- Your geo-location (from IP address)
They could theoretically also store historical data, which is essentially your full torrent history from a specific IP address.
If you’ve rather not have your torrent history linked to your IP address, it’s a good idea to use a zero-log VPN for enhanced privacy. In fact this is a best-practice for anyone using BitTorrent these days.
I personally use and recommend these VPNs for BitTorrent (in order)