How it works

A magnet link or .torrent file contains an infohash — a fingerprint of the content — and a list of trackers, servers that keep a register of who is currently sharing it.

A check sends a scraperequest to each tracker. A scrape asks a single question — “how many peers do you know of for this infohash?” — and gets back three numbers: seeders (peers with the complete file), leechers (peers still downloading) and completed (finished downloads recorded over time).

No peer is contacted, no piece of content is requested, and nothing is downloaded.

• Alive — at least one seeder is online. The download should complete.
• Stale — leechers are present but no seeder is. The swarm may still complete from partial copies, or may be stuck forever.
• Dead — trackers answered and the swarm is empty.
• No answer — every tracker timed out, refused, or does not index this torrent. That is a statement about the trackers, not about the file.

The health score combines swarm size on a logarithmic scale with a confidence factor for how many trackers agreed. One tracker reporting fifty seeders scores lower than four trackers reporting the same.

Each tracker only knows the peers that announced to it. Swarms overlap heavily, so adding the numbers together would badly overstate reality. The headline figure is therefore the highest single tracker’s count, not the sum.

Counts also lag: trackers update when peers re-announce, typically every 15 to 30 minutes.

Trackers are volunteer infrastructure and they block clients that abuse them. Every outbound request from this instance passes through a politeness layer that enforces a minimum gap between requests to the same tracker, adds randomised jitter, caps concurrency per host and overall, honours the interval each tracker asks for, and stops contacting any host that starts failing until a cooldown expires.

Identical checks running at the same moment are merged into one request, and recent answers are served from cache, so repeated lookups of a popular torrent cost the tracker nothing.

Private trackers reject scrapes from clients that are not logged in, so private torrents usually report no answer. Trackers that do not implement the scrape convention are skipped rather than probed repeatedly. DHT-only magnets with no trackers are checked against this instance’s default tracker list, which will not know about every torrent.