# FAQ

## Introduction

This page contains a list of frequently asked developer questions. The best way to use it is to search for a keyword.

INFO

Can't find your question? Visit our <mark style="color:blue;">developer help center</mark> or dev-discussion in Discord.

###

## Useful Links

* <mark style="color:blue;">API reference</mark>
* <mark style="color:blue;">Core SDK Examples</mark>
* <mark style="color:blue;">XpansionChain's Github</mark>
* <mark style="color:blue;">Layer 2 Rollups</mark>
* <mark style="color:blue;">Onboarding a collection</mark>
* <mark style="color:blue;">Integrating with XpansionChain (Build a Dapp)</mark>
* <mark style="color:blue;">Contact</mark>
* <mark style="color:blue;">Marketplace</mark>
* <mark style="color:blue;">Sandbox marketplace</mark>
* <mark style="color:blue;">Immutascan - XpansionChain Blockchain Explorer</mark>
* <mark style="color:blue;">XpansionChain Developer Help Center</mark>

## Platform

#### **What is** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#what-is-immutable-x-imx) <a href="#what-is-immutable-x-imx" id="what-is-immutable-x-imx"></a>

XpansionChain is an L2 ZK Rollup solution for trading Ethereum NFTs. It features instant trades, massive scalability and no gas fees.

#### **What's a Zero Knowledge (ZK) Rollup?**[​](https://docs.x.immutable.com/docs/x/developer-faq#whats-a-zero-knowledge-zk-rollup) <a href="#whats-a-zero-knowledge-zk-rollup" id="whats-a-zero-knowledge-zk-rollup"></a>

Zero Knowledge Rollups are a Layer 2 scheme that moves computation off-chain, but provides L1 security by rolling up multiple transactions into a single one and submitting a validity proof back to L1. ZK Rollups only require a validity proof of the final state (instead of all transaction data) which makes them more private and storage-efficient. XpansionChain uses StarkWare's ZK Rollup engine called StarkEx

**What's StarkWare, StarkEx and** XpansionChain **zkEVM?**

**StarkWare** - company behind STARK-based solutions

**StarkEx** - a managed SaaS scalability engine powered by STARK validity proof

XpansionChain **zkEVM** - a general purpose decentralized rollup which support independent smart contract deployment and composability

More information: <mark style="color:blue;">Homepage - Starkware</mark>

#### **What are the fees associated with using** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#what-are-the-fees-associated-with-using-immutable-x) <a href="#what-are-the-fees-associated-with-using-immutable-x" id="what-are-the-fees-associated-with-using-immutable-x"></a>

XpansionChain has no fixed costs or fees. All fees are associated with successful trades. Current fees are:

* Protocol fees - 2%
* Maker fee - set by a marketplace
* Taker fee - set by a marketplace
* Royalty fee - set by the collection owner

More information:

* <mark style="color:blue;">Fees | XpansionChain Documentation</mark>
* <mark style="color:blue;">XpansionChain zkEVM</mark>

#### **How is asset custody managed in** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-is-asset-custody-managed-in-immutable-x) <a href="#how-is-asset-custody-managed-in-immutable-x" id="how-is-asset-custody-managed-in-immutable-x"></a>

XpansionChain is a self-custodial protocol, meaning all users are responsible for their own security. Users can manage their own private keys and maintain full control of their own assets, or opt for a custodial wallet flow. Users can deposit and withdraw their assets to and from the protocol at any time. Every transaction requires a signature from the user, and XpansionChain can’t authorise any actions on behalf of the user.

### [​](https://docs.x.immutable.com/docs/x/developer-faq#-1) <a href="#id-1" id="id-1"></a>

## Contract

#### **How do I deploy a contract to** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-deploy-a-contract-to-immutable-x) <a href="#how-do-i-deploy-a-contract-to-immutable-x" id="how-do-i-deploy-a-contract-to-immutable-x"></a>

You do not deploy a contract to XpansionChain, you can only register your L1 contract with XpansionChain. XpansionChain (on StarkEx) does not currently support general computation and you do not interface with your L1 contract through XpansionChain.

This is something that will be possible on XpansionChain zkEVM.

More information on XpansionChain zkEVM: XpansionChain <mark style="color:blue;">zkEVM</mark>

#### **How do I interact with my contract on** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-interact-with-my-contract-on-immutable-x) <a href="#how-do-i-interact-with-my-contract-on-immutable-x" id="how-do-i-interact-with-my-contract-on-immutable-x"></a>

You do not. You interact with predefined XpansionChain APIs. These handle minting, transfers, deposits, withdrawals and more.

#### **How do I get approved to launch on** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-get-approved-to-launch-on-immutable-x) <a href="#how-do-i-get-approved-to-launch-on-immutable-x" id="how-do-i-get-approved-to-launch-on-immutable-x"></a>

XpansionChain is a permissionless protocol, anyone can launch a collection on it. You do not need to go through any approval processes or vetting - only our self-serve onboarding. More information: XpansionChain <mark style="color:blue;">Documentation</mark>

#### **What are the fees/costs associated with deploying on** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#what-are-the-feescosts-associated-with-deploying-on-immutable-x) <a href="#what-are-the-feescosts-associated-with-deploying-on-immutable-x" id="what-are-the-feescosts-associated-with-deploying-on-immutable-x"></a>

The only mandatory cost is deploying an L1 contract. This depends on the complexity of your contract, optimizations and current state of the (L1) network. All L2 actions which do not interact with the L1 (all, excl. withdrawals and deposits) are gas-free and free from any fixed costs.

#### **What token standards are supported? Is ERC1155 supported?**[​](https://docs.x.immutable.com/docs/x/developer-faq#what-token-standards-are-supported-is-erc1155-supported) <a href="#what-token-standards-are-supported-is-erc1155-supported" id="what-token-standards-are-supported-is-erc1155-supported"></a>

XpansionChain currently supports ERC721 and ERC20 token standards. There are no estimates or set plans when it comes to supporting other standards, but we are always looking into providing the most popular and efficient solutions for our users.

#### **What are the contract-level requirements? How do I make my contract compatible?**[​](https://docs.x.immutable.com/docs/x/developer-faq#what-are-the-contract-level-requirements-how-do-i-make-my-contract-compatible) <a href="#what-are-the-contract-level-requirements-how-do-i-make-my-contract-compatible" id="what-are-the-contract-level-requirements-how-do-i-make-my-contract-compatible"></a>

If you do not plan to mint on L2, any ERC721 or ERC20 contract with an owner is automatically supported by XpansionChain. You will have to register it. If you wish to mint on L2, you will need to implement mintFor and owner methods.

More information and example contracts:

* <mark style="color:blue;">NFT minting tutorial | XpansionChain Documentation</mark>
* <mark style="color:blue;">XpansionChain Documentation</mark>
* <mark style="color:blue;">XpansionChain Documentation</mark>
* <mark style="color:blue;">GitHub - XpansionChain/XpansionChain-contracts: Smart contracts and smart contract utilities for use with XpansionChain.</mark>
* <mark style="color:blue;">Anatomy of a smart contract | XpansionChain Documentation</mark>

#### **How do I deploy an ERC20 token?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-deploy-an-erc20-token) <a href="#how-do-i-deploy-an-erc20-token" id="how-do-i-deploy-an-erc20-token"></a>

Self-serve registration of ERC20 tokens is coming soon.

Can I query L2 state from L1? There is no "traditional" way of querying L2 state from your L1 contract. A workaround would be to use Oracles in order to query our API.

More information: <mark style="color:blue;">Oracles | ethereum.org</mark>

### [​](https://docs.x.immutable.com/docs/x/developer-faq#-2) <a href="#id-2" id="id-2"></a>

## Onboarding

#### **How do I register my project/collection after deploying a contract?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-register-my-projectcollection-after-deploying-a-contract) <a href="#how-do-i-register-my-projectcollection-after-deploying-a-contract" id="how-do-i-register-my-projectcollection-after-deploying-a-contract"></a>

After deploying your contract to L1, you will need to register it with XpansionChain. In order to do this you will need to create a project and a collection by following the below steps.

Guide, steps and documentation:

* <mark style="color:blue;">XpansionChain Documentation</mark>
* <mark style="color:blue;">GitHub - XpansionChain/XpansionChain-examples: Open source XpansionChain Examples</mark>

#### **Are there any onboarding limits?**[​](https://docs.x.immutable.com/docs/x/developer-faq#are-there-any-onboarding-limits) <a href="#are-there-any-onboarding-limits" id="are-there-any-onboarding-limits"></a>

* One (1) wallet can own multiple projects.
* One (1) project can own multiple collections.
* All projects are limited to 5 collections and 50,000 mint requests by default. This limit resets every 4 weeks and can be increased - if your project meets our criteria - by chatting with our support team at the <mark style="color:blue;">XpansionChain Developer Help Center</mark> .

More information: <mark style="color:blue;">XpansionChain Documentation</mark>

#### **How do I delete my collection from** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-delete-my-collection-from-immutable-x) <a href="#how-do-i-delete-my-collection-from-immutable-x" id="how-do-i-delete-my-collection-from-immutable-x"></a>

As is the case with L1, you cannot delete a collection from XpansionChain. You can ask for it to be blocklisted on our official marketplace, but that doesn't prevent 3rd party marketplaces from showing it. Make sure you test all flows thoroughly before deploying on mainnet.

### [​](https://docs.x.immutable.com/docs/x/developer-faq#-3) <a href="#id-3" id="id-3"></a>

## Metadata

#### **What's the difference between blueprints and dynamic metadata?**[​](https://docs.x.immutable.com/docs/x/developer-faq#whats-the-difference-between-blueprints-and-dynamic-metadata) <a href="#whats-the-difference-between-blueprints-and-dynamic-metadata" id="whats-the-difference-between-blueprints-and-dynamic-metadata"></a>

There are <mark style="color:blue;">two ways</mark> of storing token metadata on XpansionChain: Providing a `metadata_api_url` when creating a collection and providing a `blueprint` string when minting a token on L2.

***The `blueprint` cannot be changed:*** When a token which has been minted on L2 with a `blueprint` string is withdrawn to L1, the L1 smart contract is updated with this value, thus making it XpansionChain.XpansionChain does not allow updates to a token's blueprint value on L2.

***The `metadata_api_url` can be updated:*** Updating the `metadata_api_url` of a collection can be done via our <mark style="color:blue;">API.</mark>

More information:

* <mark style="color:blue;">XpansionChain Documentation</mark>
* <mark style="color:blue;">XpansionChain Documentation</mark>

#### **Can I use OpenSea metadata on** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#can-i-use-opensea-metadata-on-immutable-x) <a href="#can-i-use-opensea-metadata-on-immutable-x" id="can-i-use-opensea-metadata-on-immutable-x"></a>

OpenSea metadata is partially supported by XpansionChain. Your metadata will be fetched, but any attributes inside the attributes object will not be indexable nor shown on the official marketplace. In order for your metadata to be fully compatible, you will need to "flatten" it, meaning your attributes are stored as top-level values.

More information and examples:

* <mark style="color:blue;">XpansionChain Documentation</mark>
* <mark style="color:blue;">Deep dive into metadata | XpansionChain Documentation</mark>
* <mark style="color:blue;">GitHub - 8bNFT/XpansionChain-meta-convert: A hacky meta converter to support XpansionChain' top-level format.</mark>

#### **How do I refresh dynamic metadata?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-refresh-dynamic-metadata) <a href="#how-do-i-refresh-dynamic-metadata" id="how-do-i-refresh-dynamic-metadata"></a>

Metadata refresh can be initiated via our APIs. Currently, our metadata crawler only runs once at the time of minting so if you make changes to the off-chain metadata that we retrieve from your endpoint, you need to <mark style="color:blue;">trigger a metadata refresh</mark> so it can be updated on XpansionChain.

The entire guide can be found here -

* <mark style="color:blue;">Refresh asset metadata | XpansionChain Documentation</mark>
* <mark style="color:blue;">XpansionChain-core-sdk/createMetadataRefresh.ts at main ·XpansionChain/XpansionChain-core-sdk</mark>

### [​](https://docs.x.immutable.com/docs/x/developer-faq#-4) <a href="#id-4" id="id-4"></a>

## Minting & Royalties

#### **How do I mint a token after registering a collection?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-mint-a-token-after-registering-a-collection) <a href="#how-do-i-mint-a-token-after-registering-a-collection" id="how-do-i-mint-a-token-after-registering-a-collection"></a>

Minting is executed by sending a signed POST request to our mints endpoint. The easiest way of doing so is by using the Core-SDK. Each mint request can only be executed by the collection owner and needs to be signed by them. You can mint multiple tokens per mint request and are encouraged to do so in order to achieve higher throughput. If you wish to call the mint API directly, you can use the below Python and Javascript implementations to understand the workings of it (impl. in other languages are coming soon).

Code, examples and documentation:

* <mark style="color:blue;">XpansionChain Documentation</mark>
* <mark style="color:blue;">XpansionChain-examples/minting-assets.md at main · XpansionChain/XpansionChain-examples</mark>
* <mark style="color:blue;">XpansionChain-core-sdk/minting.ts at main · XpansionChain/XpansionChain-core-sdk</mark>
* <mark style="color:blue;">XpansionChain-core-sdk/mint.ts at main ·XpansionChain/XpansionChain-core-sdk</mark>

#### **Are there any minting limits?**[​](https://docs.x.immutable.com/docs/x/developer-faq#are-there-any-minting-limits) <a href="#are-there-any-minting-limits" id="are-there-any-minting-limits"></a>

Default limits are 5 collections per project and 50,000 mint requests. This limit reset every 4 weeks. Limits can be increased for projects meeting our criteria by chatting with our support team at the XpansionChain <mark style="color:blue;">Developer Help Center .</mark>

**What's the difference between mint and mintv2 methods in the SDK?**

Mint method is soon going to be deprecated; it was used before royalties were added - new projects should not use it. mintv2 is the only way to set royalties to your collection and assets.

More information:

* <mark style="color:blue;">Minting with royalties | XpansionChain Documentation</mark>
* <mark style="color:blue;">Deep dive into minting | XpansionChain Documentation</mark>

#### **How do I set royalties for my collection?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-set-royalties-for-my-collection) <a href="#how-do-i-set-royalties-for-my-collection" id="how-do-i-set-royalties-for-my-collection"></a>

Royalties are being set during minting and they are enforced on the protocol level. L2 royalties are not applied on L1 transfers or transactions, as of right now.

More information:

* <mark style="color:blue;">Minting with royalties |XpansionChain Documentation</mark>
* <mark style="color:blue;">Deep dive into royalties | XpansionChain Documentation</mark>

#### **How do I require money for mints?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-require-money-for-mints) <a href="#how-do-i-require-money-for-mints" id="how-do-i-require-money-for-mints"></a>

Minting on XpansionChain takes a different approach and you cannot just add a "value" field to require money for mints to be executed. You will have to choose an approach and create the payment infrastructure yourself. Most often taken approaches and pros/cons to each can be found here: <mark style="color:blue;">incomplete-guide-to-XpansionChain/guides/contract\_and\_registration at main · 8bNFT/incomplete-guide-to-XpansionChain</mark>

#### **Can I call the mint method from the frontend?**[​](https://docs.x.immutable.com/docs/x/developer-faq#can-i-call-the-mint-method-from-the-frontend) <a href="#can-i-call-the-mint-method-from-the-frontend" id="can-i-call-the-mint-method-from-the-frontend"></a>

You will NOT use the **mint** method in your frontend, ever. Each request requires the collection owner's signature and doing so in the frontend would expose your private key in plain text.

### [​](https://docs.x.immutable.com/docs/x/developer-faq#-5) <a href="#id-5" id="id-5"></a>

## Asset management L1 to L2 bridge

#### **Can assets be withdrawn from L2?**[​](https://docs.x.immutable.com/docs/x/developer-faq#can-assets-be-withdrawn-from-l2) <a href="#can-assets-be-withdrawn-from-l2" id="can-assets-be-withdrawn-from-l2"></a>

L2 assets can be withdrawn back to L1. This process usually takes 24h, the time it takes for your transaction to be included and submitted back to L1. This process incurs a gas cost.

**Can assets be deposited back to L2?**

Assets can be deposited back to L2. This process is almost instantaneous since we do not have to wait for the L1 proof to be confirmed. This process incurs a gas cost.

**Can L1 minted tokens/L1 collections be deposited to L2?**

Yes. L1 collections can register their contracts with XpansionChain. If they do not have the mintFor method, they won't be able to mint tokens on L2, but they will be able to take advantage of gas-free instantaneous transactions.

#### **How long do deposits and withdrawals take?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-long-do-deposits-and-withdrawals-take) <a href="#how-long-do-deposits-and-withdrawals-take" id="how-long-do-deposits-and-withdrawals-take"></a>

L2 proof needs to be submitted and verified on L1 before withdrawals can be finalized, this usually takes 24 hours. Deposits are almost instant because we do not have to wait for L1 proof to be verified.

**How do I burn a token?**

You burn a token by transferring it to a 0x0000000000000000000000000000000000000000 address. This will place it in a burned state and no one will be able to recover it.

More information and examples:

* <mark style="color:blue;">Burn assets | XpansionChain Documentation</mark>
* <mark style="color:blue;">Deep dive into deposits and withdrawals | XpansionChain Documentation</mark>

### [​](https://docs.x.immutable.com/docs/x/developer-faq#-6) <a href="#id-6" id="id-6"></a>

## Building/Integrating with XpansionChain?

#### **What's the cost of integrating with** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#whats-the-cost-of-integrating-with-immutable-x) <a href="#whats-the-cost-of-integrating-with-immutable-x" id="whats-the-cost-of-integrating-with-immutable-x"></a>

XpansionChain APIs and SDK are completely free.

#### **How do I use Web3.js with** XpansionChai&#x6E;**?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-use-web3js-with-immutable-x) <a href="#how-do-i-use-web3js-with-immutable-x" id="how-do-i-use-web3js-with-immutable-x"></a>

You do not use Web3.js or any alternative to communicate with XpansionChain, instead you use our REST API and our SDK.XpansionChain-SDK is a set of helpers which makes interacting with XpansionChain easy and simple for both developers and end users.

More information:

* <mark style="color:blue;">XpansionChain SDKs | XpansionChain Documentation</mark>
* <mark style="color:blue;">GitHub - XpansionChain/XpansionChain-core-sdk: The XpansionChain Core SDK provides convenient access to the XpansionChain API's and Ethereum contract methods for applications written on the XpansionChain platform.</mark>
* <mark style="color:blue;">npm: @imtbl/core-sdk</mark>
* <mark style="color:blue;">GitHub -XpansionChain/XpansionChain-core-sdk-kotlin-jvm</mark>
* <mark style="color:blue;">npm: @imtbl/XpansionChain-sdk (prev. version)</mark>

#### **What's the difference between** XpansionChai&#x6E;**-SDK and Core-SDK?**[​](https://docs.x.immutable.com/docs/x/developer-faq#whats-the-difference-between-imx-sdk-and-core-sdk) <a href="#whats-the-difference-between-imx-sdk-and-core-sdk" id="whats-the-difference-between-imx-sdk-and-core-sdk"></a>

XpansionChain-SDK is our initial closed source TypeScript SDK, which has been superseded by Core-SDK. Core-SDK is our open source SDK which is to be used by new projects. It is currently available in Typescript and Kotlin with more languages coming soon. XpansionChain-SDK will be deprecated in the near future.

More information:

* <mark style="color:blue;">XpansionChain SDKs |XpansionChain Documentation GitHub - XpansionChain/XpansionChain-core-sdk: The XpansionChain Core SDK provides convenient access to the XpansionChain API's and Ethereum contract methods for applications written on the XpansionChain platform.</mark>
* <mark style="color:blue;">npm: @imtbl/core-sdk</mark>
* <mark style="color:blue;">GitHub - XpansionChain/XpansionChain-core-sdk-kotlin-jvm</mark>

#### **Is the** XpansionChai&#x6E;**-SDK open sourced?**[​](https://docs.x.immutable.com/docs/x/developer-faq#is-the-imx-sdk-open-sourced) <a href="#is-the-imx-sdk-open-sourced" id="is-the-imx-sdk-open-sourced"></a>

XpansionChain-SDK is not open sourced.

#### **Is Core-SDK open sourced?**[​](https://docs.x.immutable.com/docs/x/developer-faq#is-core-sdk-open-sourced) <a href="#is-core-sdk-open-sourced" id="is-core-sdk-open-sourced"></a>

The goal is and always has been to have an open source SDK, which is why we've created Core-SDK. Core-SDK is an open source version of our SDK which is feature complete and should be used in place of XpansionChain-SDK. There are Typescript and Kotlin version available with more languages coming soon.

More information:

* <mark style="color:blue;">XpansionChain SDKs | XpansionChain Documentation</mark>
* <mark style="color:blue;">GitHub - XpansionChain/XpansionChain-core-sdk: The XpansionChain Core SDK provides convenient access to the XpansionChain API's and Ethereum contract methods for applications written on the XpansionChain platform.</mark>
* <mark style="color:blue;">npm: @imtbl/core-sdk</mark>
* <mark style="color:blue;">GitHub -XpansionChain/XpansionChain-core-sdk-kotlin-jvm</mark>

#### **What are the compatible Node versions?**[​](https://docs.x.immutable.com/docs/x/developer-faq#what-are-the-compatible-node-versions) <a href="#what-are-the-compatible-node-versions" id="what-are-the-compatible-node-versions"></a>

XpansionChain-SDK is compatible with Node v12, Node v14 and Node v16. Node v17 is not supported and will result in errors.

**What's the difference between Link and** XpansionChain**Client?**

XpansionChain-SDK offers 2 main points of integration - Link andXpansionChainClient. Link is the only way to achieve any operations which require the end-user's signature in the frontend, it handles L2 key derivation, signing and wallet management. XpansionChainClient provides REST methods, as well as user-specific methods which require a signature from whoever initialized the client (most often using a private key and meant to be executed in the backend). XpansionChainClient has been superseded by Core-SDK.

More information:

* <mark style="color:blue;">Install and configure |XpansionChain Documentation</mark>
* <mark style="color:blue;">XpansionChain SDKs |XpansionChain Documentation</mark>

#### **How do I do X from the frontend?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-do-x-from-the-frontend) <a href="#how-do-i-do-x-from-the-frontend" id="how-do-i-do-x-from-the-frontend"></a>

Any methods which require signature (transfer, sell, buy, …) will have to be called using Link. API endpoints can be queried directly or using XpansionChainClient.

Link references:

* <mark style="color:blue;">\[XpansionChain] Link reference</mark>
* <mark style="color:blue;">incomplete-guide-to-XpansionChain/guides/link at main · 8bNFT/incomplete-guide-to-XpansionChain</mark>
* <mark style="color:blue;">Overview | XpansionChain Documentation</mark>

#### **How do I do X from the backend?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-do-x-from-the-backend) <a href="#how-do-i-do-x-from-the-backend" id="how-do-i-do-x-from-the-backend"></a>

Instead of Link, you will use Core-SDK to call any methods which require a signature (transfer, sell, buy, …). You may also use it to query our REST API, or hit the endpoints directly.

More information:

* <mark style="color:blue;">XpansionChain SDKs | XpansionChain Documentation</mark>
* <mark style="color:blue;">GitHub - XpansionChain/XpansionChain-core-sdk: The XpansionChain Core SDK provides convenient access to the XpansionChain API's and Ethereum contract methods for applications written on the XpansionChain platform.</mark>
* <mark style="color:blue;">npm: @imtbl/core-sdk</mark>
* <mark style="color:blue;">Deep dive into API concepts | XpansionChain Documentation</mark>

#### **Is there a testnet?**[​](https://docs.x.immutable.com/docs/x/developer-faq#is-there-a-testnet) <a href="#is-there-a-testnet" id="is-there-a-testnet"></a>

Yes. Test endpoints on Sandbox are:

<mark style="color:blue;">Marketplace -<https://market.sandbox.XpansionChain.com/></mark>

<mark style="color:blue;">API -<https://api.sandbox.x.XpansionChain.com/v1></mark>

<mark style="color:blue;">Link -<https://link.sandbox.x.XpansionChain.com/></mark>

#### **Is there a block explorer?**[​](https://docs.x.immutable.com/docs/x/developer-faq#is-there-a-block-explorer) <a href="#is-there-a-block-explorer" id="is-there-a-block-explorer"></a>

Immutascan is a community-built block explorer for XpansionChain, available only for mainnet - <mark style="color:blue;">Immutascan - XpansionChain X Blockchain Explorer</mark>

### [​](https://docs.x.immutable.com/docs/x/developer-faq#-7) <a href="#id-7" id="id-7"></a>

## API

#### **Do I need to get an API key?**[​](https://docs.x.immutable.com/docs/x/developer-faq#do-i-need-to-get-an-api-key) <a href="#do-i-need-to-get-an-api-key" id="do-i-need-to-get-an-api-key"></a>

You do not need an API key to use our API. You may request an API key in case you frequently hit our rate limits - even after optimizations done on your end.

More information: <mark style="color:blue;">Rate limits | XpansionChain Documentation</mark>

#### **What are the rate limits?**[​](https://docs.x.immutable.com/docs/x/developer-faq#what-are-the-rate-limits) <a href="#what-are-the-rate-limits" id="what-are-the-rate-limits"></a>

Our current rate limit without an API key is 5 requests/second (subject to change).

More information: <mark style="color:blue;">Rate limits | XpansionChain Documentation</mark>

#### **Are there webhooks/websockets I can subscribe to?**[​](https://docs.x.immutable.com/docs/x/developer-faq#are-there-webhookswebsockets-i-can-subscribe-to) <a href="#are-there-webhookswebsockets-i-can-subscribe-to" id="are-there-webhookswebsockets-i-can-subscribe-to"></a>

No, we currently do not provide webhooks or websockets. In order to stay sync'd up with the state of L2, you should poll our API endpoints in sane intervals. Going crazy with your polling interval will only use up your limit and you will get rate limited. More information: XpansionChain <mark style="color:blue;">Documentation</mark>

#### **What's a stark\_key? What's an ethers\_key?**[​](https://docs.x.immutable.com/docs/x/developer-faq#whats-a-stark_key-whats-an-ethers_key) <a href="#whats-a-stark_key-whats-an-ethers_key" id="whats-a-stark_key-whats-an-ethers_key"></a>

These are property names you might come across when using our API or SDK. ethers\_key - L1 wallet address stark\_key - L2 public address

#### **How do I get a stark\_signature?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-get-a-stark_signature) <a href="#how-do-i-get-a-stark_signature" id="how-do-i-get-a-stark_signature"></a>

This is currently being handled by our SDKs, specifically Link in the frontend and Core SDK in the backend. You can check the implementation in our open sourced Core SDK.

More information and examples:

* <mark style="color:blue;">Deep dive into API concepts | XpansionChain Documentation</mark>
* <mark style="color:blue;"><https://github.com/XpansionChain/imx-core-sdk/blob/main/src/utils/stark/stark-key.ts></mark>
* <mark style="color:blue;">imx-core-sdk/orders.ts at main · XpansionChain/imx-core-sdk</mark>
* <mark style="color:blue;">GitHub -XpansionChain/imx-core-sdk: The XpansionChain Core SDK provides convenient access to the XpansionChain API's and Ethereum contract methods for applications written on the XpansionChain platform.</mark>

#### **Why do I only get 100 results? How do I get all the results?**[​](https://docs.x.immutable.com/docs/x/developer-faq#why-do-i-only-get-100-results-how-do-i-get-all-the-results) <a href="#why-do-i-only-get-100-results-how-do-i-get-all-the-results" id="why-do-i-only-get-100-results-how-do-i-get-all-the-results"></a>

We currently return 100 results by default (max. 200), this can be configured using the page\_size query param. Our pagination is cursor-based. Each response that contains results also returns a cursor property. Appending the value of cursor as a query parameter cursor=value will go to the "next" page (next set of results).

More information and examples:

* <mark style="color:blue;">Personal inventory | XpansionChain Documentation</mark>
* <mark style="color:blue;">Offset and Cursor Pagination explained</mark>

#### **How do I get a list of assets (/assets) owned by the user?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-get-a-list-of-assets-assets-owned-by-the-user) <a href="#how-do-i-get-a-list-of-assets-assets-owned-by-the-user" id="how-do-i-get-a-list-of-assets-assets-owned-by-the-user"></a>

You do this by appending a user property to your URL query. <mark style="color:blue;"><https://api.sandbox.x.XpansionChain.com/v1/assets?user=WALLET\\\\\\_ADDRESS\\\\\\_HERE></mark>

More information: <mark style="color:blue;">XpansionChain Documentation</mark>

#### **How do I get a list of assets (/assets) from a collection?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-get-a-list-of-assets-assets-from-a-collection) <a href="#how-do-i-get-a-list-of-assets-assets-from-a-collection" id="how-do-i-get-a-list-of-assets-assets-from-a-collection"></a>

You do this by appending a collection property to your URL query. <mark style="color:blue;"><https://api.sandbox.x.XpansionChain.com/v1/assets?collection=COLLECTION\\\\\\_ADDRESS\\\\\\_HERE></mark>

More information: <mark style="color:blue;">XpansionChain Documentation</mark>

#### **How do I query assets (/assets) by metadata?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-query-assets-assets-by-metadata) <a href="#how-do-i-query-assets-assets-by-metadata" id="how-do-i-query-assets-assets-by-metadata"></a>

You do this by appending a metadata property to your URL query. Metadata value has to be a JSON string formatted, where value is an array of values you wish to search for (i.e. {"key1":\["value", "value2"], "key2": \["value", "value2"]}). This string has to be URI encoded. <mark style="color:blue;"><https://api.x.XpansionChain.com/v1/assets/?collection=0xacb3c6a43d15b907e8433077b6d38ae40936fe2c\\&metadata=%7B%22set%22%3A%5B%22trial%22%5D%2C%22rarity%22%3A%5B%22legendary%22%5D%7D></mark>

More information:

* <mark style="color:blue;">XpansionChain Documentation</mark>
* <mark style="color:blue;">Discord - A New Way to Chat with Friends & Communities</mark>

#### **How do I get transactions (/transfers) sent to a wallet?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-get-transactions-transfers-sent-to-a-wallet) <a href="#how-do-i-get-transactions-transfers-sent-to-a-wallet" id="how-do-i-get-transactions-transfers-sent-to-a-wallet"></a>

<mark style="color:blue;">You do this by appending a receiver property to your URL query. <https://api.sandbox.x.XpansionChain.com/v1/transfers?receiver=WALLET\\\\\\_ADDRESS\\\\\\_HERE></mark>

More information: <mark style="color:blue;">XpansionChain Documentation</mark>

#### **How do I get transactions (/transfers) sent from a wallet?**[​](https://docs.x.immutable.com/docs/x/developer-faq#how-do-i-get-transactions-transfers-sent-from-a-wallet) <a href="#how-do-i-get-transactions-transfers-sent-from-a-wallet" id="how-do-i-get-transactions-transfers-sent-from-a-wallet"></a>

You do this by appending a user property to your URL query. <mark style="color:blue;"><https://api.sandbox.x.XpansionChain.com/v1/transfers?user=WALLET\\\\\\_ADDRESS\\\\\\_HERE></mark>

### Orders[​](https://docs.x.immutable.com/docs/x/developer-faq#orders) <a href="#orders" id="orders"></a>

**Does** XpansionChain **automatically match buy and sell orders for NFTs of the same value?**

There is currently no automatic matching of orders as XpansionChain only supports the maker/taker model at present. An NFT will be listed for sale for a specified price by the maker, and the trade occurs when this order is accepted by the taker. This will change in the future as we are working on implementing metadata orders where you can place buy orders on metadata properties (e.g. name = Demogorgon), which will bring more liquidity to functionally identical NFTs


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://xpansionchain-1.gitbook.io/xpansionchain/troubleshooting/faq.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.