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0.5.0-rc7 • Public • Published

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A JavaScript library for crypto-native ecommerce: buying, selling, and bidding on any cryptogood. With OpenSea.js, you can easily build your own native marketplace for your non-fungible tokens, or NFTs. These can be ERC-721 or ERC-1155 items. You don't have to deploy your own smart contracts or backend orderbooks.

Published on GitHub and npm


This is the JavaScript SDK for OpenSea, the largest marketplace for crypto collectibles. It allows developers to access the official orderbook, filter it, create buy orders (offers), create sell orders (auctions), create collections of assets to sell at once (bundles), and complete trades programmatically.

For the first time, you can build a cryptocommerce dapp.

You get started by instantiating your own seaport. Then you can create orders off-chain or fulfill orders on-chain, and listen to events (like ApproveAllAssets or WrapEth) in the process.

Happy seafaring! ⛵️


We recommend switching to Node.js version 8.11 to make sure common crypto dependencies work. Execute nvm use, if you have Node Version Manager.

Then, in your project, run:

npm install --save opensea-js

Install web3 too if you haven't already.

If you run into an error while building the dependencies and you're on a Mac, run this:

xcode-select --install # Install Command Line Tools if you haven't already. 
sudo xcode-select --switch /Library/Developer/CommandLineTools # Enable command line tools 
sudo npm explore npm -g -- npm install node-gyp@latest # (Optional) update node-gyp 

Getting Started

To get started, create a new OpenSeaJS client, called an OpenSeaPort 🚢, using your Web3 provider:

import * as Web3 from 'web3'
import { OpenSeaPort, Network } from 'opensea-js'
// This example provider won't let you make transactions, only read-only calls:
const provider = new Web3.providers.HttpProvider('')
const seaport = new OpenSeaPort(provider, {
  networkName: Network.Main

NOTE: Using the sample Infura provider above won't let you authorize transactions, which are needed when approving and trading assets and currency. To make transactions, you need a provider with a private key or mnemonic set.

In a browser with web3 or an extension like MetaMask or Dapper, you can use window.ethereum (or window.web3.currentProvider for legacy mobile web3 browsers) to access the native provider. In a Node.js script, you can follow this example to use a custom mnemonic.

Making Offers

Then, you can do this to make an offer on an asset:

// Token ID and smart contract address for a non-fungible token:
const { tokenId, tokenAddress } = YOUR_ASSET
// The offerer's wallet address:
const accountAddress = "0x1234..."
const offer = await seaport.createBuyOrder({
  // Value of the offer, in units of the payment token (or wrapped ETH if none is specified):
  startAmount: 1.2,
  // Read below for other options

When you make an offer on an item owned by an OpenSea user, that user will automatically get an email notifying them with the offer amount, if it's above their desired threshold.

Bidding on Multiple Assets

You can also make an offer on a bundle of assets. This could also be used for creating a bounty for whoever can acquire a list of items. Here's how you do it:

const assets = YOUR_ASSETS
const offer = await seaport.createBundleBuyOrder({
  tokenIds: => a.tokenId),
  tokenAddresses: => a.tokenAddress),
  startAmount: 2.4,
  // Optional expiration time for the order, in Unix time (seconds):
  expirationTime: ( / 1000 + 60 * 60 * 24) // One day from now

When you bid on multiple assets, an email will be sent to the owner if a bundle exists on OpenSea that contains the assets. In the future, OpenSea will send emails to multiple owners if the assets aren't all owned by the same wallet.

Making Auctions

To sell an asset, call createSellOrder. You can do a fixed-price sale, where startAmount is equal to endAmount, or a declining Dutch auction, where endAmount is lower and the price declines until expirationTime is hit:

// Expire this auction one day from now.
// Note that we convert from the JavaScript timestamp (milliseconds):
const expirationTime = ( / 1000 + 60 * 60 * 24)
const auction = await seaport.createSellOrder({
  startAmount: 3,
  // If `endAmount` is specified, the order will decline in value to that amount until `expirationTime`. Otherwise, it's a fixed-price order:
  endAmount: 0.1,

The units for startAmount and endAmount are Ether, ETH. If you want to specify another ERC-20 token to use, see Using ERC-20 Tokens Instead of Ether.

See Listening to Events to respond to the setup transactions that occur the first time a user sells an item.

Running Crowdsales

You can now sell items to users without having to pay gas to mint them!

To create a presale or crowdsale and create batches of sell orders for a single asset factory, first follow the tutorial for creating your crowdsale contract.

Then call createFactorySellOrders with your factory contract address and asset option identifier, and set numberOfOrders to the number of assets you'd like to let users buy and mint:

// Expire these auctions one day from now
const expirationTime = ( / 1000 + 60 * 60 * 24)
const sellOrders = await seaport.createFactorySellOrders({
  // Will create 100 sell orders in parallel batches of 10, to speed things up:
  numberOfOrders: 100

Here's an example script you can use to mint items.

NOTE: If numberOfOrders is greater than 5, we will automatically batch them in groups of 5 so you can post orders in parallel. Requires an apiKey to be set during seaport initialization in order to not be throttled by the API.

Games using this method include Coins & Steel and a couple in stealth :) If you have questions or want support, contact us at (or in Discord).

Fetching Orders

To retrieve a list of offers and auction on an asset, you can use an instance of the OpenSeaAPI exposed on the client. Parameters passed into API filter objects are underscored instead of camel-cased, similar to the main OpenSea API parameters:

import { OrderSide } from 'opensea-js/lib/types'
// Get offers (bids), a.k.a. orders where `side == 0`
const { orders, count } = await seaport.api.getOrders({
  asset_contract_address: tokenAddress,
  token_id: token_id,
  side: OrderSide.Buy
// Get page 2 of all auctions, a.k.a. orders where `side == 1`
const { orders, count } = await seaport.api.getOrders({
  asset_contract_address: tokenAddress,
  token_id: token_id,
  side: OrderSide.Sell
}, 2)

Note that the listing price of an asset is equal to the currentPrice of the lowest valid sell order on the asset. Users can lower their listing price without invalidating previous sell orders, so all get shipped down until they're cancelled or one is fulfilled.

To learn more about signatures, makers, takers, listingTime vs createdTime and other kinds of order terminology, please read the Terminology Section of the API Docs.

The available API filters for the orders endpoint is documented in the OrderJSON interface below, but see the main API Docs for a playground, along with more up-to-date and detailed explanantions.

   * Attrs used by orderbook to make queries easier
   * More to come soon!
  maker?: string, // Address of the order's creator
  taker?: string, // The null address if anyone is allowed to take the order
  side?: OrderSide, // 0 for offers, 1 for auctions
  owner?: string, // Address of owner of the order's asset
  sale_kind?: SaleKind, // 0 for fixed-price, 1 for Dutch auctions
  asset_contract_address?: string, // Contract address for order's asset
  token_id?: number | string,
  token_ids?: Array<number | string>,
  listed_after?: number | string, // This means listing_time > value in seconds
  listed_before?: number | string, // This means listing_time <= value in seconds
  // For pagination
  limit?: number,
  offset?: number,

Buying Items

To buy an item , you need to fulfill a sell order. To do that, it's just one call:

const order = await seaport.api.getOrder({ side: OrderSide.Sell, ... })
const accountAddress = "0x..." // The buyer's wallet address, also the taker
await this.props.seaport.fulfillOrder({ order, accountAddress })

If the order is a sell order (order.side === OrderSide.Sell), the taker is the buyer and this will prompt the buyer to pay for the item(s).

Accepting Offers

Similar to fulfilling sell orders above, you need to fulfill a buy order on an item you own to receive the tokens in the offer.

const order = await seaport.api.getOrder({ side: OrderSide.Buy, ... })
const accountAddress = "0x..." // The owner's wallet address, also the taker
await this.props.seaport.fulfillOrder({ order, accountAddress })

If the order is a buy order (order.side === OrderSide.Buy), then the taker is the owner and this will prompt the owner to exchange their item(s) for whatever is being offered in return. See Listening to Events below to respond to the setup transactions that occur the first time a user accepts a bid.

Transferring Items (Gifting)

A handy feature in OpenSea.js is the ability to transfer any supported asset (not just non-fungible tokens) in one line of JavaScript.

To transfer an ERC-721 asset or an ERC-1155 asset, it's just one call:

const transactionHash = await seaport.transferOne({
  asset: { tokenId, tokenAddress },
  fromAddress, // Must own the asset

To transfer other types of assets, like ENS names, you can pass in a WyvernAsset as the asset, set a schemaName, and set isWyvernAsset to true. For more information, check out the documentation for WyvernSchemas on

Affiliate Program

New in version 0.4, OpenSea.js allows to you easily create an affiliate program in just a few lines of JavaScript! It's the crypto-equivalent of bounty hunting 💰

You can use this to win at least 1% of the sale price of any listing, both for assets and bundles. You can also allow users to win bounties by referring your items for sale.

Referring Listings

You can instantly create an affiliate program for your assets by just passing in one more parameter when fulfilling orders! Whenever someone refers a sale or the acceptance of an offer, you can add a referrerAddress to give their wallet credit:

const referrerAddress = "0x..." // The referrer's wallet address
await this.props.seaport.fulfillOrder({ order, accountAddress, referrerAddress })

This works for buying assets and bundles, along with accepting bids.

OpenSea will send the referrer an email congradulating them, along with 1% of the item's sale price.

Custom Referral Bounties

Sellers can customize the bounties they add to their items when listing them for sale. By default, OpenSea will pay referrers 1% and sellers pay them nothing, but sellers can increase this up to the full OpenSea fee (currently 2.5% for most assets) for both assets and bundles:

// Price the Genesis CryptoKitty at 100 ETH
const startAmount = 100
// Reward referrers with 10% of the final sale price,
// or 10 ETH in this case
const extraBountyPercent = 10
// The final bounty will be 10% + 1% from OpenSea, or 11 ETH!
const auction = await seaport.createSellOrder({
  tokenAddress: "0x06012c8cf97bead5deae237070f9587f8e7a266d", // CryptoKitties
  tokenId: "1", // Token ID
  accountAddress: OWNERS_WALLET_ADDRESS,
  extraBountyBasisPoints: extraBountyPercent * 100

NOTE: The final bounty in the example above will be 10% from the seller plus 1% from OpenSea, or 11 ETH in total!

Developers can request to increase the OpenSea fee to allow for higher bounties - by default, it's capped at 2.5%. If you have any questions, contact us at (or in Discord), or join the program at


Interested in making bundling items together or making bids in different ERC-20 tokens? OpenSea.js can help with that.

Bulk Transfers

A handy feature in OpenSea.js is the ability to transfer multiple items at once in a single transaction. This works by grouping together as many transferFrom calls as the Ethereum gas limit allows, which is usually under 30 items, for most item contracts.

To make a bulk transfer, it's just one call:

const assets: Array<{tokenId: string; tokenAddress: string}> = [...]
const transactionHash = await seaport.transferAll({
  fromAddress, // Must own all the assets

This will automatically approve the assets for trading and confirm the transaction for sending them.

Creating Bundles

You can also create bundles of assets to sell at the same time! If the owner has approved all the assets in the bundle already, only a signature is needed to create it.

To make a bundle, it's just one call:

const assets: Array<{tokenId: string; tokenAddress: string}> = [...]
const bundle = await seaport.createBundleSellOrder({
  bundleName, bundleDescription, bundleExternalLink,
  assets, accountAddress, startAmount, endAmount,
  expirationTime, paymentTokenAddress

The parameters bundleDescription, bundleExternalLink, and expirationTime are optional, and endAmount can equal startAmount, similar to the normal createSellOrder functionality.

The parameter paymentTokenAddress is the address of the ERC-20 token to accept in return. If it's undefined or null, the amount is assumed to be in Ether.

Wait what, you can use other currencies than ETH?

Using ERC-20 Tokens Instead of Ether

New in version 0.3: now you can make auctions and offers in whatever ERC-20 token you want! Just specify the token's contract address as the paymentTokenAddress when creating the order.

Here's an example of listing the Genesis CryptoKitty for $100! No more needing to worry about the exchange rate:

// Token address for the DAI stablecoin, which is pegged to $1 USD
const paymentTokenAddress = "0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359"
// The units for `startAmount` and `endAmount` are now in DAI, so $100 USD
const auction = await seaport.createSellOrder({
  tokenAddress: "0x06012c8cf97bead5deae237070f9587f8e7a266d", // CryptoKitties
  tokenId: "1", // Token ID
  accountAddress: OWNERS_WALLET_ADDRESS,
  startAmount: 100,

You can use getFungibleTokens to search for tokens by symbol name. And you can even list all orders for a specific ERC-20 token by querying the API:

const token = await seaport.getFungibleTokens({ symbol: 'MANA'})[0]
const order = await seaport.api.getOrders({
  side: OrderSide.Sell,
  payment_token_address: token.address

Fun note: all ERC-20 tokens are allowed! This means you can create crazy offers on crypto collectibles using your own ERC-20 token. However, will only display offers and auctions in ERC-20 tokens that it knows about, optimizing the user experience of order takers. Orders made with the following tokens will be shown on OpenSea for the near future:

Private Auctions

Now you can make auctions and listings that can only be fulfilled by an address of your choosing. This allows you to negotiate a price in some channel and sell for your chosen price on OpenSea, without having to trust that the counterparty will abide by your terms!

Here's an example of listing a Decentraland parcel for 10 ETH with a specific buyer address allowed to take it. No more needing to worry about whether they'll give you enough back!

// Address allowed to buy from you
const buyerAddress = "0x123..."
const listing = await seaport.createSellOrder({
  tokenAddress: "0xf87e31492faf9a91b02ee0deaad50d51d56d5d4d", // Decentraland
  tokenId: "115792089237316195423570985008687907832853042650384256231655107562007036952461", // Token ID
  accountAddress: OWNERS_WALLET_ADDRESS,
  startAmount: 10,

Sharing Sale Fees with OpenSea

We share fees for successful sales with game developers, relayers, and affiliates using the OpenSea orderbook. Developers can customize the fee amount to apply to buyers and/or sellers.

See Affiliate Program above for how to register referrers for sales.

More information will appear here when our redesigned affiliate program is ready. In the meantime, contact us at (or in Discord), or use our legacy affiliate program at

Listening to Events

Events are fired whenever transactions or orders are being created, and when transactions return receipts from recently mined blocks on the Ethereum blockchain.

Our recommendation is that you "forward" OpenSea events to your own store or state management system. Here's an example of doing that with a Redux action:

import { EventType } from 'opensea-js'
import * as ActionTypes from './index'
import { openSeaPort } from '../globalSingletons'
// ...
handleSeaportEvents() {
  return async function(dispatch, getState) {
    openSeaPort.addListener(EventType.TransactionCreated, ({ transactionHash, event }) => {{ transactionHash, event })
      dispatch({ type: ActionTypes.SET_PENDING_TRANSACTION_HASH, hash: transactionHash })
    openSeaPort.addListener(EventType.TransactionConfirmed, ({ transactionHash, event }) => {{ transactionHash, event })
      // Only reset your exchange UI if we're finishing an order fulfillment or cancellation
      if (event == EventType.MatchOrders || event == EventType.CancelOrder) {
        dispatch({ type: ActionTypes.RESET_EXCHANGE })
    openSeaPort.addListener(EventType.TransactionDenied, ({ transactionHash, event }) => {{ transactionHash, event })
      dispatch({ type: ActionTypes.RESET_EXCHANGE })
    openSeaPort.addListener(EventType.TransactionFailed, ({ transactionHash, event }) => {{ transactionHash, event })
      dispatch({ type: ActionTypes.RESET_EXCHANGE })
    openSeaPort.addListener(EventType.InitializeAccount, ({ accountAddress }) => {{ accountAddress })
      dispatch({ type: ActionTypes.INITIALIZE_PROXY })
    openSeaPort.addListener(EventType.WrapEth, ({ accountAddress, amount }) => {{ accountAddress, amount })
      dispatch({ type: ActionTypes.WRAP_ETH })
    openSeaPort.addListener(EventType.UnwrapWeth, ({ accountAddress, amount }) => {{ accountAddress, amount })
      dispatch({ type: ActionTypes.UNWRAP_WETH })
    openSeaPort.addListener(EventType.ApproveCurrency, ({ accountAddress, tokenAddress }) => {{ accountAddress, tokenAddress })
      dispatch({ type: ActionTypes.APPROVE_WETH })
    openSeaPort.addListener(EventType.ApproveAllAssets, ({ accountAddress, proxyAddress, tokenAddress }) => {{ accountAddress, proxyAddress, tokenAddress })
      dispatch({ type: ActionTypes.APPROVE_ALL_ASSETS })
    openSeaPort.addListener(EventType.ApproveAsset, ({ accountAddress, proxyAddress, tokenAddress, tokenId }) => {{ accountAddress, proxyAddress, tokenAddress, tokenId })
      dispatch({ type: ActionTypes.APPROVE_ASSET })
    openSeaPort.addListener(EventType.CreateOrder, ({ order, accountAddress }) => {{ order, accountAddress })
      dispatch({ type: ActionTypes.CREATE_ORDER })
    openSeaPort.addListener(EventType.OrderDenied, ({ order, accountAddress }) => {{ order, accountAddress })
      dispatch({ type: ActionTypes.RESET_EXCHANGE })
    openSeaPort.addListener(EventType.MatchOrders, ({ buy, sell, accountAddress }) => {{ buy, sell, accountAddress })
      dispatch({ type: ActionTypes.FULFILL_ORDER })
    openSeaPort.addListener(EventType.CancelOrder, ({ order, accountAddress }) => {{ order, accountAddress })
      dispatch({ type: ActionTypes.CANCEL_ORDER })

To remove all listeners and start over, just call seaport.removeAllListeners().

Learning More

Auto-generated documentation for each export is available here.

If you need extra help, support is free! Contact the OpenSea devs. They're available every day on Discord in the #developers channel.

Example Code

Check out the Ship's Log, built with the SDK, which shows the recent orders in the OpenSea orderbook.

You can view a live demo here! Also check out the Mythereum marketplace, which is entirely powered by OpenSea.js.

Development Information


Node >= v8.11.2 required.

Before any development, install the required NPM dependencies:

npm install


Then, lint and build the library into the lib directory:

npm run build

Or run the tests:

npm test

Note that the tests require access to both Infura and the OpenSea API. The timeout is adjustable via the test script in package.json.

Generate Documentation

Generate html docs, also available for browsing here:

npm run docsHtml

Or generate markdown docs available for browsing on git repos:

npm run docsMarkdown

Due to a markdown theme typescript issue, docs just generates html docs right now:

npm run docs


Contributions welcome! Please use GitHub issues for suggestions/concerns - if you prefer to express your intentions in code, feel free to submit a pull request.


npm i opensea-js

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