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Bubs testnet

Bubs testnet

Bubs Testnet is a the first OP Stack testnet with Celestia underneath hosted by Caldera with support from Celestia Labs. Bubs is dedicated to providing developers with an EVM-compatible execution layer to deploy their EVM applications on.

Built with the OP Stack and Celestia

The Bubs Testnet is a testnet rollup, a modified version of optimism-bedrock that uses Celestia as a data availability (DA) layer. This integration can be found in the @celestiaorg/optimism repository. The testnet is hosted by Caldera, who makes it easy to launch rollups with no code required. Bubs' data is posted to Celestia on the Mocha testnet. View the namespace for Bubs on Celestia's Mocha testnet.

Learn more about the setup of the integration in the introduction.

Building on Bubs

Bubs Testnet provides a robust environment for developers to test their Ethereum Virtual Machine (EVM) applications. It offers an EVM-compatible execution layer, making it an ideal platform for developers looking to build and test applications in a setting that closely mirrors an OP Stack rollup on Celestia.

Learn more at


Remote Procedure Call (RPC) URLs are endpoints that allow developers to interact with the blockchain. They are essential for sending transactions, querying blockchain data, and performing other interactions with the blockchain.

For the Bubs Testnet, you can connect to the following RPC URLs:




  • wss://

This URL serves as the entry point to the Bubs Testnet. You can use it in your applications to connect to the testnet and interact with the smart contracts you deploy there.

Remember, Bubs Testnet is a testing environment!


Bridging is a process that enables the transfer of assets between different blockchains.

To bridge between Ethereum Sepolia and Bubs Testnet, visit the Bubs Testnet bridge.


To visit the Bubs testnet faucet, go to and click the "Faucet" tab.


To visit the explorer, go to


To see the status and uptime information for Bubs, visit the status page.

Next steps

Now that you have a better understanding of the Bubs Testnet and its integration of OP Stack and Celestia, you can start exploring its capabilities.