1inch Orderbook API is using the 1inch [Limit Order Protocol](https://github.com/1inch/limit-order-protocol), which is a set of smart contracts that can work on any EVM-based blockchains. Key features of the protocol are extreme flexibility and high gas efficiency.

## Orderbook

An orderbook is a trading mechanism where users create fixed-price orders for tokens, specifying both the execution price and an expiration condition that limits how long the order remains valid.
For example, you can put up 2 WBTC tokens for sale at the price of 82,415 DAI tokens valid for 7 days.

The 1inch Limit Orders Protocol provides a rich set of tools for flexible and professional trade management:

- Partial fill
  Orders can be filled in multiple steps without requiring full execution at once.
- Predicates
  Conditional execution logic (e.g. price bounds, time constraints, external state checks).
- Single cancellation
  Cancel a specific order by its unique hash.
- Batch (bunch) cancellation
  Invalidate multiple orders efficiently in a single action.
- Fullness check
  Ensure the order is filled exactly as specified, preventing over- or under-fills when required.
- Validation
  Custom on-chain validation logic to control whether an order can be executed.

To enable efficient market making, RFQ orders are used, benefiting from a special optimization that avoids high gas costs during execution.

## Limit order execution

### 1. Order placement

Users place limit orders. Each order is cryptographically signed and remains off-chain until executed.

### 2. Order discovery

Anyone can fetch these signed orders using the [1inch Orderbook API](./methods) to execute trades by submitting them on-chain.

### 3. Order execution

To execute an order, the signed order is submitted to the smart contract's `fillOrder` method. See the latest contract addresses in [Limit Order SDK](https://github.com/1inch/limit-order-sdk/blob/master/src/constants.ts).

:::info
Both the buyer and seller must approve the 1inch Limit Order Protocol to transfer their tokens.
:::

## Supported tokens standards

- ERC-20
- ERC-721
- ERC-1155

Other token standards can be supported via external extensions.

:::info
For workloads that require higher RPS, expanded quotas, or sustained performance, explore the available paid plans on the [**pricing page**](/pricing).
For organizations with significant trading volumes or advanced requirements, [**complete this application**](/get-enterprise) to explore tailored Enterprise options.

:::

## Supported Chains

| Supported Chains | Chain ID |
| :--------------- | :------- |
| Ethereum         | 1        |
| Base             | 8453     |
| Binance          | 56       |
| zkSync           | 324      |
| Gnosis           | 100      |
| Optimism         | 10       |
| Polygon          | 137      |
| Linea            | 59144    |
| Sonic            | 146      |
| Unichain         | 130      |
| Arbitrum         | 42161    |
| Avalanche        | 43114    |

## More resources

- To quickly understand how to create, sign, and submit a limit order, see the
  [Quickstart guide](./quick-start.md).
- For detailed information about each endpoint, refer to the [Orderbook API Swagger section](./methods).
- Try directly at [1inch dApp](https://1inch.com/pro?mode=limit&pair=1:0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2-0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48).
- Explore the [Limit Order Protocol](https://github.com/1inch/limit-order-protocol/).
- For integration purposes, check out [Limit Order SDK](./limit-order-sdk/introduction.md).