> ## Documentation Index
> Fetch the complete documentation index at: https://etherspot.fyi/llms.txt
> Use this file to discover all available pages before exploring further.

# Arka testnet Usage

## Using Arka

When estimating a transaction with the SDK on testnets we support
we can pass in the testnet api key value as **'etherspot\_public\_key'**
and set the mode of the transaction to be sponsored like so:

```javascript theme={null}
try {
const CHAIN_ID = 11155111;
const API_KEY = 'etherspot_public_key'; // replace this with your api key
const op = await primeSdk.estimate({ 
    url: `https://rpc.etherspot.io/paymaster?apiKey=${API_KEY}&chainId=${CHAIN_ID}&useVp=true`,
    context: { mode: 'sponsor' } 
    });
} catch(err) {
    console.log(err);
}
```

### Supported testnets

* Sepolia
* Base Sepolia
* Scroll Sepolia
* Fuse Sparknet
* Ancient8 Testnet
* Flare Coston2
* Rootstock testnet

This will use testnet funds and a paymaster we have specifically
setup for devs to test out before trying sponsored transactions on mainnet.