Introduction to 0x

This documentation describes the public infrastructure we are building - 0x Protocol, API, DAO - to make assets more accessible and liquid and empower teams around the world to build a new financial system. Learn more about our mission and values. 
Prefer to watch a video instead? Jump to 0x Concept Videos. 
The 0x Ecosystem 
0x is an open-source, decentralized exchange infrastructure that enables the exchange of tokenized assets on multiple blockchains.

The 0x protocol is, at its core, a set of secure smart contracts that facilitate the peer-to-peer exchange of Ethereum-based assets. The protocol serves as an open standard and common building block for any developer needing exchange functionality. 

In addition to the externally-audited smart contracts, 0x also offers developer tools tailored to the ecosystem and open-access to a pool of shared liquidity.
Developers can integrate with 0x at the smart contract or application layer.

The diagram below shows an overview of the 0x ecosystem, which includes applications who provide liquidity (supply), applications who consume liquidity (demand), and the multiple supported blockchains. 
0x is an open-source, decentralized exchange infrastructure that enables the exchange of tokenized assets on multiple blockchains.
Makers and Takers
Within the 0x ecosystem, there are two sides - Makers and Takers: 
Supply (aka Makers)
This is the entity who creates 0x orders and provides liquidity into the system for the Demand side (Takers) to consume. 0x aggregates liquidity from multiple sources including:
On-chain liquidity - DEXs, AMMs (e.g. Uniswap, Curve, Bancor)
Off-chain liquidity - Professional Market Makers, 0x's Open Orderbook network
Relevant Docs:
​Market Makers - Professional Market Making With Limit Orders
​0x API Orderbook - Sharing Limit Orders
​Limit Orders (Advanced Traders) -  Filling and Managing Limit Orders
Demand (aka Takers)
This is the entity who wants the Maker's asset. The Takers agree to trade their asset for the Maker's asset; in other words, they consume the 0x liquidity. Examples include projects such as MetaMask, Coinbase, and dydx.
Relevant Docs:
​0x API Swap - Programatically execute a ERC20 token trade
​NFT Support - NFT Limit Orders (ERC721 + ERC1155)
Governance
In addition to Makers and Takers is the 0x Community DAO, which is the collective governing voice of the 0x protocol and the ZRX token. 
Relevant Docs: 
​Governance​
0x Protocol, API, and DApps
The 0x API allows applications to tap into the 0x protocol for ERC20<>ERC20 swaps. 
The NFT Swap SDK is a developer tool that enables ERC20<>ERC721 and ERC20<>ERC1155 swaps in just a few lines of code. 
0x Protocol
At the core of 0x is the 0x Protocol, a set of audited smart contracts that are deployed on Ethereum and 6 other EVM chains and L2 networks (as of Feb 2022). These smart contracts enable the trading of ERC20, ERC721, and ERC1155 assets.
0x API
The 0x API is the interface that allows DeFi developers to tap into the 0x Protocol. It has 2 major endpoints - /swap and /orderbook. 
The /swap endpoint allows users to fetch available quotes across the liquidity supply. The API aggregates liquidity from on-chain and off-chain networks and uses smart order routing to split up a transaction across decentralized exchange networks to be filled with the lowest slippage possible while minimizing transaction costs. 
The /orderbook endpoint lets applications and users access 0x's open orderbook liquidity, and post limit orders making them publicly available immediately. Orderbook API replaces the 'SRA' API, without introducing breaking changes as all endpoints are backward compatible.

NFT Swap SDK
The NFT Swap SDK was built and maintained by Trader.xyz, an ecosystem partner. It is a  library written in Typescript that allows developers to quickly integrate NFT swap functionality into their app. It leverages the NFT features in the 0x protocol v4. 
Applications
Applications, which includes both Makers and Takers, integrate with the 0x API or NFT Swap SDK or directly access the protocol’s smart contracts to take action on the best prices.
How does 0x work?
Let’s look into how a 0x order is executed.
1.A Maker creates a 0x order which is a json object that adheres to a standard order message format. It indicates what kind of asset the Maker is committed to trade. Assets could include fungible tokens (ERC20), non-fungible tokens (ERC721), or bundles of assets (ERC1155).
2.The order is hashed, and the Maker signs the order to cryptographically commit to the order they authored.
3.The order is shared with counter-parties.
If the Maker of the 0x order already knows their desired counter-party, they can send the order directly (via email, chat, or over-the-counter platform)
If the Maker doesn’t know a counter-party willing to take the trade, they can submit the order to orderbook. 
4.0x API aggregates liquidity across all the sources to surface the best price for the order to the Taker. 0x helps traders create, find, and fill the 0x orders through the paradigm of off-chain relay and on-chain settlement. This means that 0x does not store orders on the blockchain; instead, orders are stored off-chain, and trade settlement only occurs on-chain. This unique feature makes 0x a flexible and gas-efficient DEX protocol for developers to build on.
5.The Taker fills the 0x order by submitting the order and the amount they will fill it for to the blockchain.
6.The 0x protocol’s settlement logic verifies the Maker’s digital signature and that all the conditions of the trade are satisfied. If so, the assets involved are atomically swapped between Maker and Taker. If not, the trade is reverted.
What can I build on 0x?
0x is an open-source project, which opens it up for anyone to freely use it as a liquidity lego in their product.
Projects can be built on 0x. In addition, 0x can also be integrated into any existing application where exchange is not the core purpose of the application. Below are some project ideas. For more examples, see The "comprehensive" list of projects section in this article.
Demand (Takers)
Exchanges
A decentralized exchange for X asset on Y market
An Ebay-style marketplace for digital goods
An over-the-counter (OTC) trading desk
Wallets
Digital wallets whose users want to exchange tokens
Options and derivatives
A DeFi protocol that needs liquidity and exchange to function (e.g., a derivatives, lending, or options protocol)
Portfolio managers
Prediction markets
Non-fungible tokens (NFT)
NFT marketplace
Games with in-game currencies or items
Investment strategies
Data
0x multi-chain analytics portal
Real-time trades panel w/ GraphQL wrappers
Counter/twitter bot of positive slippage returned to users
Supply (Makers)
Orderbook models
Automatic Market Makers (AMM) models
Market Makers
A market making or arbitrage trading bot

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The 0x Ecosystem

Makers and Takers

Governance

0x Protocol, API, and DApps

How does 0x work?

What can I build on 0x?

Demand (Takers)

Supply (Makers)