You can test an Ocean Protocol application (such as a marketplace) against the test networks (testnets) described below. This page is a brief overview of those testnets. The [tutorials](/tutorials/) cover more details (e.g. how to connect to specific ones).
By default, [Barge](https://github.com/oceanprotocol/barge) will deploy a local "Spree Testnet" on your machine: a local testnet not connected to any external public testnet.
When running a Spree Testnet, you can connect to a node at RPC URL [http://localhost:8545](http://localhost:8545) (called "Localhost 8545" in MetaMask).
Spree Testnet details can be found in the [Barge README.md file](https://github.com/oceanprotocol/barge#spree-network). You can configure the Spree nodes by editing the files in the `barge/networks/spree/` directory.
> Note: Spree testnets are named after the Spree River, the main river flowing through Berlin, Germany, where many Ocean Protocol developers are located.
There is a Nile blockchain explorer at [https://submarine.dev-ocean.com/](https://submarine.dev-ocean.com/). You can use it to check the status of a transaction, the balance of an account, and more. It uses the following symbols for Nile Ether and Nile Ocean Tokens:
If you run [Barge](https://github.com/oceanprotocol/barge) with the `--local-nile-node` option, then Barge will run a Nile node on your local machine (along with everything else Barge runs). There might be many blocks in the Nile Testnet's blockchain, so it might take a long time for your local Nile node to sync, i.e. to download a local copy of all the blocks. **In the meantime, the local Nile node won't be able to do certain things.**
The [Kovan Testnet](https://github.com/kovan-testnet/proposal) (or just "Kovan") is a public Ethereum Testnet operated by members of the Ethereum community.
The Ocean Protocol keeper contracts are deployed to the Kovan Testnet.
There are some Kovan blockchain explorers, e.g. [Etherscan for Kovan](https://kovan.etherscan.io/) and [BlockScout for Kovan](https://blockscout.com/eth/kovan). You can use those to check the status of a transaction, the balance of an account, and more.
### Ocean Components Connected to Kovan
There is a [Secret Store](/concepts/components/#secret-store) connected to the Kovan Testnet for use by Ocean Protocol projects (including your projects). It's operated by BigchainDB GmbH. Its URL is:
Aside from the Secret Store, there is no other Ocean Protocol software component (e.g. Aquarius) that is live, connected to the Kovan Testnet, and operated by BigchainDB GmbH.
### Using Barge with Kovan
If you run [Barge](https://github.com/oceanprotocol/barge) with the the `--local-kovan-node` option, then Barge will run a Kovan node on your local machine (along with everything else Barge runs). There are many blocks in the Kovan Testnet's blockchain, so it can take a long time for your local Kovan node to sync, i.e. to download a local copy of all the blocks. **In the meantime, the local Kovan node won't be able to do certain things.**
Note: You shouldn't use a Ganache-Based Testnet unless you know why you're doing so. For example, a Ganache-based testnet can be used to test some smart contracts, but it can't be used with a Secret Store.
The Duero Testnet is similar to the Nile Testnet, but it's only for internal use by the Ocean Protocol dev team. They test new things in the Duero Testnet before deploying them in the Nile Testnet (which is for use by anyone). That is, the testing order is Spree (local), Duero (private), Nile (public).
If you need to know something technical about the Duero Testnet, such as the RPC URL, please contact the Ocean Protocol dev team.
