Ethereum: ETH, Gas Fees and ERC-20 Tokens Explained
What Ethereum is, how gas fees and ERC-20 tokens work, and how the Chaingateway API sends and receives both without running a node.
Ethereum is a public blockchain that runs smart contracts — code stored on-chain that executes exactly as written — and settles two kinds of value on top of that: ETH, its native currency, and tokens built inside ETH-denominated contracts under standards like ERC-20. This page covers what that means in practice: who pays gas, how a token transfer differs from an ETH transfer, and how proof-of-stake finality works. For the technical integration itself, the Chaingateway Ethereum API sends and receives both over REST, without a synced node or a library like web3.js behind your code.
What Ethereum settles: ETH and tokens
Ethereum settles ETH itself and tokens that live inside ETH-denominated smart contracts. ERC-20 is the token standard behind USDT, USDC, DAI and thousands of other assets — a shared contract interface (balanceOf, transfer, approve) that lets any wallet or exchange interact with any compliant token the same way. ERC-721 and ERC-1155 extend the same contract model to non-fungible and multi-token assets. Our ERC-20 token standard guide covers the format in more depth, and the ERC-20 address guide explains how an address and a token contract differ.
Gas: who pays, and how much
Every Ethereum transaction costs gas, paid in ETH by the sending address — never the recipient. A plain ETH transfer costs a fixed 21,000 gas; an ERC-20 transfer runs contract code and costs a multiple of that, varying by token. Since the London upgrade (EIP-1559), the price per unit of gas splits into a base fee the network burns and a priority tip to the block proposer, and both rise when the network is busy. A wallet holding tokens but no ETH cannot send them, because the token contract has no way to cover its own execution cost — the wallet needs ETH alongside its token balance. Receiving ETH or a token costs the recipient nothing; gas becomes relevant only when funds move back out, including when a treasury wallet sweeps deposits in from customer addresses.
In the Chaingateway API, gas limit, gas price and the EIP-1559 fee caps (maxFeePerGas, maxPriorityFeePerGas) are optional fields on a transaction request. Leave them out and the API sets them when it builds and broadcasts your transaction; pass them when you want the fee pinned.
Proof of stake: block times and finality
Ethereum has run on proof of stake since the Merge. Blocks arrive in fixed twelve-second slots, 32 slots form a 6.4-minute epoch, and a block finalizes after roughly two epochs — about 13 minutes — once two-thirds of staked ETH has attested to it (protocol parameters as of mid-2026). Finalized means the network cannot revert the block without destroying a large share of all staked ETH. A transfer is typically included in a block within seconds to a minute; each further slot adds assurance. Most applications credit ordinary-sized deposits after inclusion plus a handful of blocks and reserve the full 13-minute wait for large amounts — the deposit webhook gives you the on-chain event, and where the crediting line sits is a policy decision in your own code.
Sending and receiving Ethereum over REST
Webhooks
Register a callback URL and get an HTTPS notification, signed with an X-Signature header, when a deposit settles. Delivery has no built-in automatic retry — failed notifications are listed by GET /api/v2/ethereum/webhooks/notifications/failed and can be re-sent with one call.
Easy transactions
Send ETH and ERC-20 tokens with gas limit, gas price and nonce as optional request fields. Supply the recipient, the token and the amount, and the API fills in the rest, or pin the fee fields yourself when you want control.
Secure address handling
Address format is validated on every request, and existing keys come in through POST /api/v2/ethereum/addresses/import, password-protected and stored encrypted. The architecture is non-custodial.
Decoded queries
Transactions come back as readable JSON through GET /api/v2/ethereum/transactions/{txid}/decoded, so your application reads structured fields instead of parsing raw contract output.
Get started in three steps
Create an account and copy your API key from the dashboard. The 7-day trial starts without a credit card or KYC.
Call GET /api/account to confirm the key works, then create an address or import an existing one under POST /api/v2/ethereum/addresses/import.
Add the header X-Network: testnet, fund the address from a public Sepolia faucet, and send a test ERC-20 transfer. Register a webhook, then drop the header — the same code runs on mainnet.
Ethereum, Polygon and Arbitrum: one request shape
The ERC-20 request pattern Ethereum uses repeats on the other EVM chains the API covers: /api/v2/polygon/transactions/erc20 and /api/v2/arbitrum/transactions/erc20 take the same fields as Ethereum's own route, and BNB Smart Chain uses /api/v2/bsc/transactions/bep20. Code written against Ethereum ports to Polygon or Arbitrum by editing the path, which matters when mainnet gas makes a small transfer uneconomical. The full chain list is on the blockchain API overview.
Frequently asked questions
Ready to build on Ethereum?
Create an account at app.chaingateway.io/register and send a Sepolia ERC-20 transfer within the trial. The full endpoint reference is in the Ethereum API docs, and plans and rate limits are on their own page.