📜 Validium Validium
An Ethereum layer-2 that proves transactions are correct with a zero-knowledge validity proof, but keeps the transaction data off-chain instead of posting it to Ethereum. That trade-off buys cheaper fees and more throughput.
🧾 The simple version — a notarized receipt
Picture a notary stamping a public record to say “this deal is legitimate and the numbers add up.” Anyone can trust the stamp. But the detailed paperwork isn't published — it sits in a private filing cabinet. A validium works the same way. A validity proof is the public stamp on Ethereum that the transactions were processed correctly, while the actual transaction data stays off-chain. You get something cheaper and lighter, but you depend on whoever holds the cabinet to let you retrieve your records.
🔁 How a validium actually runs
- 📨 You send a transaction to an off-chain operator instead of straight to Ethereum
- 📦 The operator batches and runs many transactions together, away from the main chain
- 🔐 It creates a validity proof (a zero-knowledge proof) plus a short summary of the new state
- ⟠ Only the proof and summary go on-chain. An Ethereum contract verifies the proof — the raw data never appears
- 🗄️ A Data Availability Committee (DAC) — a set of trusted parties — holds the off-chain data and signs to confirm they have it
📊 In StarkEx, the DAC has 8 members who attest they're storing the data. These are vendor figures shared for illustration, not a fixed rule for every validium.
⚖️ Validium vs zk-rollup — one choice, big difference
This is the easiest way to lock in the idea. A zk-rollup and a validium use the same kind of validity proof to guarantee correctness. They differ in exactly one place: where the transaction data lives.
| 🧱 zk-rollup | 📜 validium | |
|---|---|---|
| Validity proof on Ethereum | ✅ Yes | ✅ Yes |
| Transaction data | 📤 Posted on-chain | 🗄️ Kept off-chain |
| Fees & throughput | Higher fees, lower throughput | Lower fees, higher throughput |
| Data trust assumption | None — data is on-chain | You trust the committee to keep the data |
There's also a middle option called Volition. With Volition, you pick per transaction whether your data goes on-chain (rollup-style safety) or off-chain (validium-style cheapness). Same app, your call each time.
🚀 Why anyone uses it
Posting every transaction's data to Ethereum is the expensive part. By keeping data off-chain, a validium shrinks its on-chain footprint, which means lower fees and far higher throughput. StarkEx in validium mode claims 9,000+ transactions per second, versus a practical ceiling closer to 2,000 for on-chain rollups — again, vendor numbers meant to show the gap, not a benchmark you should quote as fact.
🌍 Where you'll meet one
- 🛠️ StarkEx by StarkWare — the most prominent validium engine; it can run in zk-rollup OR validium mode. It powers apps on StarkNet's wider ecosystem
- 🎮 Immutable X — an NFT and gaming layer-2 built on StarkEx, known for $0 gas to mint and trade
- 🧪 zkPorter (Matter Labs / zkSync) — a hybrid that borrows the off-chain data idea
🚨 What a beginner should keep in mind
- 🗄️ Data availability is the catch — if the committee loses or withholds the data, you may not be able to prove your balance or withdraw
- 🤝 Extra trust — a validium adds a trust assumption that a true zk-rollup doesn't have
- 💸 Great for cheap, high-volume use — gaming, NFTs, and trading where low fees matter more than maximum security
❓ FAQ
- Is a validium just as safe as a zk-rollup?
- Not quite. The validity proof stops any invalid transaction from being processed, so the math is just as solid. But the transaction data sits off-chain with a committee. If that committee withholds or loses the data, you might not be able to prove your balance and your funds could be stuck. A validium asks you to trust the data holders in a way a zk-rollup does not.
- What is the one difference between a validium and a zk-rollup?
- Where the transaction data lives. A zk-rollup posts the data on-chain to Ethereum; a validium keeps it off-chain. Both prove correctness with the same kind of zero-knowledge validity proof. That single choice about data is the whole difference.
- Where would a beginner run into a validium?
- Usually inside NFT, gaming, or trading apps that advertise near-zero gas fees for minting or trading. Many of those run on StarkEx in validium mode. You may be using one without ever seeing the word 'validium'.