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).
The [Kovan Testnet](https://github.com/kovan-testnet/proposal) (or just "Kovan") is a public Ethereum Testnet operated by members of the Ethereum community.
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.
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.
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:
- Secret Store at [https://secret-store.dev-ocean.com](https://secret-store.dev-ocean.com)
- Aquarius at [https://nginx-aquarius.dev-ocean.com](https://nginx-aquarius.dev-ocean.com)
- Brizo at [https://nginx-brizo.dev-ocean.com](https://nginx-brizo.dev-ocean.com)
- Jupyter Hub at [https://mantaray.dev-ocean.com](https://mantaray.dev-ocean.com)
- [Token Bridge Frontend](https://github.com/oceanprotocol/bridge-ui) (for a token bridge between Nile and Kovan) at [https://token-bridge.dev-ocean.com](https://token-bridge.dev-ocean.com)
When Ocean Protocol developers run [Barge](https://github.com/oceanprotocol/barge) with the `--local-spree-node` option, a "Spree Testnet" is deployed on their local machine: a local testnet not connected to any external public testnet.
Spree Testnet details can be found in the [Barge README.md file](https://github.com/oceanprotocol/barge/blob/develop/README.md). 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.