# Resources for Developers

## Reference documentation

ZKsync documentation: <https://docs.zksync.io/build>

Relevant Github repositories:

* <https://github.com/cronos-labs/cronos-zkevm>
* <https://github.com/cronos-labs/era-contracts>
* <https://github.com/zksync-sdk/zksync-ethers> (Ethers library for Javascript)

## Cronos zkEVM Mainnet URLs

* Chain ID: `388`
* Token: zkCRO ("Cronos zkEVM CRO")
* JSON RPC API (rate limited): <https://mainnet.zkevm.cronos.org>&#x20;
* WebSocket (rate limited): `wss://ws.zkevm.cronos.org`
* Blockchain explorer: <https://explorer.zkevm.cronos.org/>
* Gas price: :warning: The gas price of is currently fixed at `2500gwei`
  * This is subject to change and is expected to be dynamic in the next major release to be announced.
* Developer portal: <https://developers.zkevm.cronos.org/>
* Contract verification interface: <https://explorer.zkevm.cronos.org/verifyContract>
* Bridge for ERC-20 tokens (Ethereum <=> Cronos zkEVM): <https://zkevm.cronos.org/bridge>

***

## Cronos zkEVM Sepolia Testnet URLs

* Chain ID: `240`
* Token: zkTCRO
* JSON RPC API (rate limited): [https://testnet.zkevm.cronos.org](https://testnet.zkevm.cronos.org/)
* WebSocket (rate limited): `wss://ws.testnet.zkevm.cronos.org`
* Blockchain explorer: <https://explorer.zkevm.cronos.org/testnet>
* Gas price: :warning: The gas price of is currently fixed at 1250`gwei`
  * This is subject to change and is expected to be dynamic in the next major release to be announced.
* Developer portal: <https://developers.zkevm.cronos.org/>
* Contract verification interface: <https://explorer.zkevm.cronos.org/testnet/verifyContract>
* zkTCRO faucet: <https://zkevm.cronos.org/faucet>
* [Demo project repository](https://github.com/kentimsit/cronos-zkevm-hardhat-boilerplate) for smart contract developers
* Testnet bridge for ERC-20 tokens (zkEVM testnet <=> Ethereum Sepolia): <https://zkevm.cronos.org/bridge/testnet>

***

#### Remix Plugin for zkEVM development

Remix users can leverage the `zksync` Remix plugin for their development. The plugin simplifies writing and deploying zkEVM smart contracts, making it accessible to both newcomers and experienced users. The plugin can be activated by searching with the keywords `zksync`

<figure><img src="https://3199918912-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FuSKiKu5wNi55i329LvV2%2Fuploads%2F6XiTweZSkds1EOsyVXhl%2FScreenshot%202024-08-16%20at%2013.12.05.png?alt=media&#x26;token=3ffaeaff-dc41-4377-a3c8-e40114d8bd9b" alt="" width="375"><figcaption></figcaption></figure>

Read more: <https://medium.com/nethermind-eth/the-zksync-era-remix-plugin-a-how-to-guide-fc54e8d24bd3>