Add the network

Chain 3961 is not in wallets' built-in lists yet, so you add it once. It takes one tap from a Ferminux page, or a minute by hand.

One tap

Open ferminux.net/docs with MetaMask, Rabby or another browser wallet installed and use Add Ferminux to your wallet, or the add-network button on the explorer. The wallet shows the settings and asks you to confirm. Nothing is signed or spent.

The web wallet needs no setup: it runs on chain 3961 already, and your keys stay in your browser.

By hand

MetaMask: Settings → Networks → Add a network → Add a network manually. Rabby: More → Add custom network. Other wallets have the same five fields.

Other endpoints:

• WebSocket: wss://rpc.ferminux.net/ws
• Second HTTPS path to the same service: https://ferminux.net/rpc
• Your own node: http://127.0.0.1:8545 with the same chain ID (see Run a node)

From a dapp

The request that the Add network buttons send is the standard EIP-3085 call, whose method name is fixed by the standard:

await window.ethereum.request({
  method: "wallet_addEthereumChain",
  params: [{
    chainId: "0xF79",
    chainName: "Ferminux",
    nativeCurrency: { name: "Ferminux", symbol: "FMX", decimals: 18 },
    rpcUrls: ["https://rpc.ferminux.net"],
    blockExplorerUrls: ["https://explorer.ferminux.net"],
  }],
});

To switch a wallet that already has the network, call wallet_switchEthereumChain with [{ chainId: "0xF79" }] and fall back to the call above when it fails with code 4902.

Your first FMX

A new address holds nothing, and every transaction costs a little FMX in gas. The faucet sends 0.5 FMX to a fresh address, once per address per 24 hours:

curl -sX POST https://ferminux.net/api/faucet \
  -H 'content-type: application/json' \
  -d '{"address":"0xYourAddress"}'

GET https://ferminux.net/api/faucet shows its current limits. 0.5 FMX covers thousands of simple transfers. To buy more, see Where does FMX trade?

Tokens

FMX is the chain's own coin, like the gas coin of any network. Do not import it as a token; it appears as the network balance.

Tokens on the chain are FRC-20 contracts. Import them with Import tokens and the contract address:

Look up any other token on the explorer before adding it. Anyone can deploy a contract with a familiar name.

Common messages

"Chain ID returned by the custom network does not match." The chain ID or RPC URL is mistyped. Ferminux is 3961 in decimal and 0xF79 in hex; MetaMask's form wants the decimal. Check what an endpoint reports:

curl -s -X POST -H 'Content-Type: application/json' \
  --data '{"jsonrpc":"2.0","method":"eth_chainId","params":[],"id":1}' \
  https://rpc.ferminux.net
# {"jsonrpc":"2.0","id":1,"result":"0xf79"}

"Could not fetch chain ID." The wallet cannot reach the endpoint. Run the curl above from the same machine. For your own node, make sure it was started with --http.

"The symbol does not match." Some wallets warn about any chain missing from their built-in list. FMX with 18 decimals is correct; continue.

The transaction stays pending, or is refused as underpriced. The tip was below 1 gwei. Chain 3961's signers only include transactions that tip at least 1 gwei. Most wallets ask the network for a tip and get 1 gwei; if you edited the fee by hand, set the priority fee back to 1 gwei and use the wallet's speed-up button. More in Troubleshooting.

The base fee shows a few wei. That is correct. The chain is rarely full, so the base fee sits near its floor; almost all of what you pay is the 1 gwei tip. A transfer (21,000 gas) costs about 0.000021 FMX.

Signatures are rejected. Signing tools that assume chain 1 produce signatures for another network. Tell them chain ID 3961 (clef: --chainid 3961).