0x Protocol: Decentralized Exchange Infrastructure for Ethereum Tokens
0x is an open protocol that provides shared infrastructure for decentralized, non-custodial trading of ERC-20 and other tokens on Ethereum and EVM-compatible chains. It uses an off-chain order relay model paired with on-chain settlement through audited smart contracts, so users keep custody of their assets and only pay gas when a trade actually executes. Participants called relayers host shared order books, and the protocol aggregates liquidity across order books and automated market makers to route trades to the best available price. Its native token, ZRX, is used mainly for governance and coordinating the network of liquidity providers across the ecosystem.
0x is an open, permissionless protocol that lets developers build decentralized exchanges and liquidity applications on Ethereum and other EVM-compatible networks. Rather than running a single trading venue, 0x provides the shared infrastructure — smart contracts, order formats, and routing logic — that thousands of wallets and apps use to swap ERC-20 tokens without surrendering custody. Trades are matched off-chain through relayers and APIs, then settled on-chain by audited smart contracts. Its native asset, the ZRX token, is used for governance and protocol coordination. In short, 0x is plumbing for on-chain trading rather than an exchange you log into.
What problem does 0x solve?
Centralized exchanges concentrate every order, balance, and private key in one place. That concentration makes them convenient but also turns them into high-value targets — a single breach can drain thousands of users at once. A decentralized exchange spreads these functions across many participants and never takes custody of user funds, removing the single point of failure. If the distinction is new to you, our explainer on the differences between centralized and decentralized crypto exchanges breaks it down further.
0x was designed to make building these non-custodial venues cheap and standardized. Before shared infrastructure existed, every team that wanted on-chain trading had to write, audit, and maintain its own settlement contracts. 0x turned that into a common layer: define an order, sign it with your wallet, and let the protocol's contracts handle settlement. The result is that a swap widget inside a wallet, a portfolio app, and a standalone DEX can all tap the same liquidity.
How the 0x protocol works
The defining design choice in 0x is the split between order relay and order settlement. This "off-chain order, on-chain settlement" model keeps gas costs low while preserving trustless execution.
Off-chain orders, on-chain settlement
A maker creates an order — for example, "I will sell 1,000 token A for 500 token B" — and signs it cryptographically with their wallet. That signed order is passed around off-chain at no cost. When a taker decides to fill it, only the final trade is broadcast to the blockchain. Because order creation and cancellation happen off-chain, users avoid paying a gas fee for every quote, and only pay when a trade actually settles.
Relayers and the order book
Relayers are the participants that host and broadcast these signed orders, effectively running a shared order book. Anyone can operate a relayer, and they can charge a fee for the liquidity they surface. This is an order book-style approach, distinct from the constant-product automated market maker model that pools liquidity; if you want the full contrast, see our guide on order books versus automated market makers. Over time the protocol expanded beyond a single order-book design to aggregate liquidity across many sources, including AMM pools, so that an application can route a swap to whichever venue offers the best price.
A worked example
Suppose a trader wants to swap 10,000 USDC for ETH. The 0x routing layer scans available liquidity, finds that 70% of the order fills best on one AMM pool and 30% on a relayer's order book, and constructs a single transaction that splits the trade. The trader signs once, the settlement contract executes both legs atomically, and the funds never leave the trader's wallet until the swap clears. If the price moves beyond the trader's tolerance during execution, the slippage setting causes the transaction to revert rather than fill at a bad rate.
0x versus other DEX models
The table below contrasts 0x's design with the two most common alternatives traders encounter.
| Property | 0x protocol | Single AMM DEX | Centralized exchange |
|---|---|---|---|
| Custody of funds | Non-custodial | Non-custodial | Custodial |
| Liquidity model | Aggregated (order book + AMMs) | Single liquidity pool | Internal order book |
| Order creation cost | Off-chain, free | On-chain only at swap | Off-chain, free |
| Single point of failure | No | No | Yes |
| Native token role | ZRX governance | Often governance | None required |
| Best for | Routing across venues | Simple pair swaps | Fiat on-ramps, speed |
The practical takeaway: 0x is most valuable as an aggregation and routing layer, while a standalone AMM is simplest for a single trading pair and a centralized venue still wins on fiat access and raw matching speed.
The ZRX token
ZRX is the native asset of the 0x ecosystem. Its primary roles are governance — letting holders vote on protocol upgrades and parameter changes — and coordinating the network of market makers and liquidity providers that supply quotes. The token has a capped supply, and its circulating supply has grown toward that cap over the protocol's lifetime as allocations vested.
Like most governance assets tied to trading infrastructure, ZRX's value tends to track adoption of the underlying protocol and broader market cycles rather than direct cash flows. Treat any historical price as a snapshot, not a forecast — always check live data before acting.
Risks and pitfalls to understand
0x removes custodial risk but introduces a different risk surface that users should weigh:
- Smart-contract risk. Settlement depends on protocol contracts. A bug or exploit in those contracts can affect funds at the moment of settlement, even though balances sit in your wallet between trades.
- Relayer and routing trust. Off-chain order relay means you rely on relayers and aggregators to surface fair prices. A poorly-configured front end can route to thin liquidity and worsen execution.
- Slippage and front-running. As with any on-chain trade, large orders can move the price and be exposed to maximal extractable value strategies. Set conservative slippage limits.
- Token approvals. Granting unlimited spending allowances to a settlement contract is convenient but risky; revoke stale approvals periodically.
- Governance concentration. If ZRX voting power is concentrated, protocol decisions may not reflect the broader community.
COINOTAG perspective
We view 0x less as a single product and more as a piece of shared market infrastructure — closer to a settlement rail than to an app. For everyday users that distinction matters: you rarely interact with "0x" by name, yet the swap button inside many wallets and portfolio tools quietly routes through it. The durable value proposition is aggregation. As liquidity fragments across dozens of chains and pools, a neutral layer that finds the best route and settles non-custodially becomes more useful, not less. The open question for any infrastructure token, ZRX included, is whether protocol usage translates into sustained demand for the asset itself — a link that is rarely automatic and always worth scrutinizing.
If you are new to on-chain trading, start by understanding the difference between custodial and non-custodial venues, then learn how routing and slippage shape real execution before committing size.