04 / Limits
Where tracing gets blurry — or stops
Anyone who tells you every bitcoin is traceable is selling something — and anyone who tells you stolen coins are gone forever hasn't looked. The truth has structure: some techniques merely add friction, some genuinely destroy confidence, and a few end the public trail outright. Knowing which is which keeps expectations honest, which is the whole point of this page.
▍ENDS THE PUBLIC TRAIL
Custodial pooling
Deposit to an exchange and the coins are swept into an omnibus hot wallet with everyone else's. On-chain continuity stops at the deposit — from there, ownership exists only in the service's private ledger. The trail continues, but via subpoena, not blockchain.
Privacy-coin swaps
Stolen BTC swapped into Monero disappears from public-ledger analysis: sender, receiver, and amount are hidden at the protocol level. Records may exist at the swap service — the chain itself yields nothing further.
Lightning
Only channel opens and closes touch the chain. Payments routed inside the network leave no public record. Off-chain means exactly that.
▍DEGRADES CONFIDENCE
Mixers and tumblers
Custodial mixers take coins in and pay different coins out, severing the direct link. The caveats cut both ways: mixers keep internal records that have been seized, several have been sanctioned or dismantled, and amount-and-timing correlation sometimes re-links flows. Blurred, not always erased.
CoinJoin and PayJoin
Collaborative transactions manufacture ambiguity: equal-valued outputs with many plausible input-output mappings, no custodian involved. Naive heuristics fail outright. Research has partially unmixed some implementations, but honest post-CoinJoin attribution is probabilistic and should be labeled as such.
Chain hopping
Instant swap services and cross-chain bridges move value to other ledgers, often without KYC. Each hop is usually visible as it enters the service, then continues under that service's records. Trails survive when services cooperate — and stall when they won't.
▍PRACTICAL FRICTION
Combinatorial scale
Aggressive fan-out grows the frontier exponentially. Value-weighted pruning tames most of it (the money concentrates on few paths), but adversaries can force any fixed analysis budget to choose between breadth and depth.
Heuristic error
Clustering can over-merge; change detection can guess wrong; labels can be stale or simply mistaken. Deterministic vin→vout hops are immune — everything layered on top inherits some error rate, and honest tooling says which layer each claim lives in.
Time and monitoring
A trace is a snapshot. Unspent tainted outputs can move the minute after you stop looking, so conclusions decay without continuous monitoring of the frontier — a practical burden rather than a theoretical wall.
Why CoinJoin blinds the heuristics
What "ends" actually means
Notice what the hardest barriers have in common: the trail doesn't vanish into thin air — it passes behind a door. The exchange's ledger, the mixer's logs, the swap service's records. Public analysis stops at the door; legal process can open it. That inversion is the strategic heart of tracing: the same services that break on-chain continuity are the ones bound by and obligations — which makes them not walls but chokepoints.
Which is exactly where this guide goes next: where funds can actually be frozen.