Public chains are pseudonymous, not anonymous. Every transfer is permanently visible to anyone; what's missing is the mapping from address to human. So the whole game is attribution, and attribution almost always happens at an off-ramp — the point where value converts to fiat through a service that collected identity documents. Everything between the crime and the off-ramp is just plumbing you have to follow.

The beginner error is treating a clustering heuristic's output as fact. "These addresses belong to the same entity" is a probabilistic inference with known failure modes, and commercial attribution labels are proprietary guesses you cannot audit. Trace confidently; attribute carefully.

1. Establish the chain and address type. The string tells you. Bitcoin legacy pay-to-public-key-hash addresses begin with ; pay-to-script-hash, historically multisig and wrapped SegWit, with ; native SegWit bech32 with ; Taproot with . Ethereum and every EVM chain use plus 40 hex characters, with mixed-case acting as an EIP-55 checksum. Full table in the reference file above.

2. Open the address in a block explorer and read it properly. Balance is the least interesting field. What matters: first-seen and last-seen timestamps (activity lifespan), total received versus current balance (a swept address is a conduit, a holding address is a destination), transaction count, and the counterparty set. On EVM chains also read the internal transactions, the token transfer tab, and whether the address has code — an address with bytecode is a contract, not a person's wallet, and its behaviour is defined by that code.

3. Choose the right mental model for the chain. UTXO chains like Bitcoin have no accounts: a transaction consumes discrete unspent outputs and creates new ones, so "the balance of an address" is a derived aggregate and value visibly splits and merges. You trace coins through a graph of outputs. Account-model chains like Ethereum have balances mutated by transfers, so you trace account-to-account edges, and a single transaction can trigger a cascade of internal transfers and token movements that don't appear in the top-level view. Confusing the two is the most common source of nonsense conclusions.

5. Find the off-ramp. Exchanges assign each customer a unique deposit address, then periodically sweep those deposits into consolidated hot wallets. That sweep is the giveaway: many independent addresses funnelling into one large wallet, on a schedule, is an exchange deposit structure. Reaching a deposit address is the single most valuable outcome of a trace, because the exchange holds KYC records for whoever it belongs to — obtainable by law enforcement through legal process, not by you. Document the deposit address, the amount, the timestamp, and the exchange identification basis, and hand it over.

6. Recognise service and contract interaction by pattern. Equal-denomination outputs with many participants in one transaction is CoinJoin. Fixed-denomination deposits and later withdrawals from the same contract are a Tornado-style shielded pool. A transfer into a contract followed by an event on a different chain is a bridge. Repeated round-number transfers between two addresses on a schedule looks like payroll or a subscription, not a market operation. Peel chains — a large amount that repeatedly spends a small piece out and forwards the remainder — are a classic laundering and cash-out pattern.

CoinJoin breaks common-input ownership by design: the inputs belong to different people. Naïve clustering that ignores this merges unrelated users into one giant false cluster — a well-known and serious failure mode.

Shielded mixing pools break the deposit-withdrawal link cryptographically. What survives are the metadata leaks: an anonymity set that's small at low volume, deposit and withdrawal timing, a withdrawal whose gas is paid from an address that also funded the deposit, and users who withdraw to an address already linked to them.

Cross-chain bridges and swap services don't break linkage cryptographically but do break it practically, because they move the trail to another chain with different tooling. Amount-and-timing correlation across the two chains often re-establishes it. Instant no-account swap services are the same problem with an added custodial hop that keeps its own logs.

Privacy coins are a hard stop, not a slowdown. Ring signatures, stealth addresses and confidential amounts mean there is no public sender, no public recipient and no public amount to follow. Say so plainly rather than implying you could have gone further. On chains with optional shielding, most activity is transparent, and the leaks are at the shielded/transparent boundary.

Taint analysis after any of these is a modelling choice, not a measurement. Poison, haircut, FIFO and last-in-first-out give materially different answers on the same data, and courts in some jurisdictions impose their own rule for mixed funds. Always state which model you used. "40% tainted" without a named model is meaningless.

Attribution to a named human is never confirmed on-chain evidence alone. It becomes confirmed when an off-chain record — a subpoena return, a court filing, a signed message, an entity's own disclosure — closes the gap.

A victim reports paying an extortion demand to and provides the transaction ID.

The explorer shows one input from the victim and two outputs: 0.4137 BTC to a fresh address and a smaller amount to another. Change heuristic says the unrounded larger output is the payment and the smaller is the victim's change — but the victim confirms the demanded amount was the smaller figure, so the heuristic was backwards here. Dead end avoided only because a human corroborated it; note that in the file.

Following the extortion output: within a day it merges with eleven other inputs into a single transaction. Common-input ownership means all twelve are one controller, and the equal-value structure that would indicate CoinJoin is absent. The consolidated output forwards to an address that receives from thousands of unrelated addresses and sweeps outward on a fixed schedule — an exchange hot-wallet structure. The address immediately before it, which received only from our cluster, is the deposit address.

Graded: transaction facts confirmed; the twelve-address cluster probable; the exchange identification probable, on structure plus two independent labels; the account holder's identity unknown and only obtainable by legal process. Reported that way, with the deposit address and timestamps flagged for the victim's counsel.

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Tools and explorers by chain, with what each is actually good for, are in the explorer and tooling catalogue.

Reading a public ledger is not regulated. Acting on it can be. Sanctions authorities publish specific digital-currency addresses on their designated persons lists — the US OFAC SDN list carries them as explicit address entries — and transacting with a designated address is a strict-liability matter in many jurisdictions. Check listings before you interact with anything, and never send a "test transaction" to a subject address: it is interaction, it marks you, and it may be a violation.

Naming a person as the owner of an address is a serious public accusation with defamation exposure, and the underlying inference is probabilistic. Bulk purchase or handling of leaked exchange customer data brings data-protection obligations regardless of how it reached you; see . Where the objective is asset recovery or a criminal referral, preserve the chain of custody: record block heights, transaction IDs and capture timestamps, not screenshots of an explorer.