Part of Zcash can be traced and part cannot. Transparent transactions are public like Bitcoin's, so they can be followed. In shielded transactions the sender, recipient and amount are hidden by zero-knowledge proofs, but studies from 2017 and 2018 showed that patterns of use, such as moving coins in and out of the shielded pool, can still link activity.
How to read this guide
Every claim below names its source. Two academic studies are summarised from their published text; they describe Zcash as it was in 2017 and 2018. We did not review newer academic analyses, so nothing here says that today's pools are weaker or stronger than those studies found. Where we give our own reasoning, it is labelled as such.
What is visible, by type of transaction
| Transaction type | What an outside observer sees | Traceable? |
|---|---|---|
| Transparent to transparent | Sender address, recipient address and amount | Yes, like Bitcoin |
| Shielded to shielded | That a transaction happened and its fee; the shielded sender, recipient and amount are hidden | Contents are hidden |
| Mixed (shielding or unshielding) | The transparent side in full; the shielded side hidden | The crossing is the weak point |
The official Zcash site puts the split this way: "Shielded Zcash addresses keep your financial information private" while "Transparent addresses make that information public." For the full explanation of both address types, read shielded vs transparent transactions and the address types guide. You can test the transparent side yourself in our Zcash Explorer; a shielded address only shows that its format is valid.
What the research found
Quesnelle, 2017: round trips
Jeffrey Quesnelle's paper "On the linkability of Zcash transactions" (arXiv:1712.01210, December 2017) found that most coins sent to shielded addresses were later sent back to transparent addresses. He searched for round trips in which the same or nearly the same amount goes from a transparent address into the pool and back out to a transparent address, and argued that this pattern is highly linkable when the two steps are close in time. With that one heuristic he matched 31.5 % of all coins sent to shielded addresses.
Kappos and colleagues, 2018: founders, miners and patterns of use
"An Empirical Analysis of Anonymity in Zcash" by George Kappos, Haaroon Yousaf, Mary Maller and Sarah Meiklejohn (University College London) appeared at the USENIX Security Symposium in 2018. Its abstract concludes that "while it is possible to use Zcash in a private way, it is also possible to shrink its anonymity set considerably by developing simple heuristics based on identifiable patterns of usage."
From the paper's introduction: the authors observed that the vast majority of Zcash activity was in the transparent part of the blockchain. Because miners and founders were required to put newly generated coins into the shielded pool first, those groups were the main actors there. With heuristics that attribute deposits and withdrawals to founders and miners, the authors linked 65.6 % of the value withdrawn from the pool back to such deposits, and a general heuristic added 3.5 %. They state that these simple heuristics reduced the size of the overall anonymity set by 69.1 %.
What the studies cannot tell you about today
- Age. Kappos et al. was published in May 2018. Sapling activated on October 28, 2018 and Orchard in 2022 (see our history of Zcash), so neither pool was part of those data sets.
- Scale. The 2018 paper reported 112,235 ZEC in the shielded pool, 3.6 % of the supply at the time of writing. Our Shielded Supply tracker showed 29.21 % of supply in shielded pools on October 13, 2026. The two figures come from different counting methods and different years; they show that the situation changed, not that privacy is better or worse. For what each share measures, see how much of Zcash is shielded and Network Activity.
- Method. Heuristics work on patterns. They show what is possible with public data; they do not prove who made a given payment, and they say nothing about a person who did not follow those patterns.
What the official documentation advises
The Zcash documentation page "Privacy Recommendations and Best Practices" (written for zcashd, with a note that the warnings apply on any platform) lists these points:
- Hold funds in shielded addresses: "Store more Zcash on a shielded address than is need [sic] for any single transaction", and "the more funds held in shielded pools, the greater the overall privacy of the network."
- "Do not leak metadata such as the tx id, tx amount, or counterparty information as they can be used to create linkages."
- Fees are publicly visible, so let a privacy-focused wallet choose the fee.
- Reusing one shielded address for a single purpose is safe; using one address for several purposes "makes it possible for someone to compare the contexts" and build a profile.
- "A unique IP address can allow network observers to correlate your Zcash transactions"; advanced users may route their node through Tor.
Where traceability can still creep in
- Transparent endpoints. Anything that happens on a transparent address is public, including the transparent half of a shielding transaction. Our shielded check guide shows what an explorer can and cannot display.
- Crossing the boundary. Both studies found links where value moved between the transparent and shielded sides. Matching amounts and short gaps in time were the signal in Quesnelle's work.
- Habits. Reusing addresses across purposes, or sharing transaction IDs and amounts, hands out the linking material the documentation warns about.
- Off-chain records. This is our reasoning, not a finding of the studies: an exchange or merchant that knows who you are can see its own side of a deposit or withdrawal, whatever the chain hides.
Traceable by choice: viewing keys
Privacy in Zcash is not all-or-nothing. A viewing key lets you reveal a shielded account's activity to an auditor, accountant or tax authority you choose, without giving up control of the funds. The memo field is encrypted too, so only the recipient can read it. If you are comparing Zcash with other approaches, see Zcash vs. Bitcoin privacy and Zcash vs. Monero; this guide does not rank privacy coins. Tracing is a different question from counterfeiting; for the two documented flaws that could have allowed fake ZEC, see has Zcash ever been counterfeited?.
Sources and method
- Jeffrey Quesnelle, "On the linkability of Zcash transactions", arXiv:1712.01210, submitted December 4, 2017.
- George Kappos, Haaroon Yousaf, Mary Maller, Sarah Meiklejohn, "An Empirical Analysis of Anonymity in Zcash", USENIX Security Symposium 2018 (arXiv:1805.03180); figures read from the paper text on October 14, 2026.
- Zcash documentation, "Privacy Recommendations and Best Practices" (zcash.readthedocs.io), read October 14, 2026.
- z.cash, "What is the difference between shielded and transparent Zcash?", read October 14, 2026.
- Our own tracker: Shielded Supply, reading of October 13, 2026. See also our privacy hub and open data.
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