GLOSSARY · BLOCKCHAIN & WEB3
Mainnet
What a mainnet is: the live blockchain network where transactions have real value, how it differs from a testnet and what to check before deploying.
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What is a mainnet?
Mainnet is a blockchain's main network, the one in production: transactions on it move real value and are recorded permanently. It is the opposite of a testnet, where you test with worthless tokens. On Ethereum, mainnet is identified by chain ID 1 (Yellow Paper and EIP-155).
What does "mainnet" mean, and when did Ethereum's launch?
"Mainnet" is short for main network. Ethereum's went live on July 30, 2015 with the Frontier release, and since The Merge, on September 15, 2022, it has run on proof of stake instead of proof of work. Its upgrades are rehearsed on testnets first; the two most recent were Pectra, on May 7, 2025, and Fusaka, on December 3, 2025, according to ethereum.org's history page.
Mainnet vs. testnet
| Testnet | Mainnet | |
|---|---|---|
| Value of the tokens | None: you get them free from faucets | Real: ETH and tokens have a market price |
| Network identifier (chain ID) on Ethereum | Sepolia, 11155111; Hoodi, 560048 | 1 |
| Transaction cost | Gas paid in test ETH | Gas paid in real ETH |
| If something goes wrong | Fix it and redeploy | A deployed contract cannot be changed unless it was designed to be upgradeable, and a confirmed transfer cannot be undone |
| Network continuity | It may be reset or stop being maintained, as Goerli and Holesky were | Production network |
| What it is used for | Development, testing, pilots and rehearsing protocol upgrades | Launch and operation with real users and funds |
What changes when you deploy to mainnet?
- Real cost: every transaction pays gas in ETH, calculated as the units of gas used times the sum of the base fee, which is burned, and the priority fee (ethereum.org gas documentation).
- Immutable code: according to ethereum.org, smart contracts are immutable by design and their logic cannot be changed once deployed; to make them upgradeable you have to plan for a pattern such as a proxy from the start.
- Real users and funds: a bug can cause losses that cannot be recovered.
- Real dependencies: the oracles, stablecoins and other contracts yours interacts with have different addresses on mainnet and on testnet.
Checklist before moving to mainnet
- Automated tests for every function, including edge cases and expected failures.
- A full rehearsal on testnet with the same deployment script you will use on mainnet, plus end-to-end tests with the real wallet and front end.
- A code audit by an independent team, and fixes for whatever it finds: smart contract audit.
- Permissions reviewed: who is owner or admin, who can mint, pause or upgrade, and whether those keys sit in a multisig.
- Mainnet parameters: chain ID, addresses of external contracts (oracles, stablecoins) and gas limits, which differ from the testnet ones.
- After deployment: source code verified on the block explorer and an incident response plan.
Mainnet and regulated tokenization
Deploying to mainnet does not change what the token is legally. If it is a financial instrument, in the EU it is still governed by MiFID II, not MiCA (Art. 2(4)(a) of Regulation (EU) 2023/1114). That is why, in a regulated token issuance, the testnet pilot also lets the issuer and its intermediaries validate investor onboarding and transfer restrictions before issuing on the main network.
Official sources: Ethereum Yellow Paper (mainnet chain ID); EIP-155; ethereum.org: Ethereum history; ethereum.org: Ethereum networks; ethereum.org: gas and fees; ethereum.org: upgrading smart contracts; Regulation (EU) 2023/1114, MiCA (EUR-Lex).
Framework verified as of October 15, 2026. At Unknown Gravity we prepare the move to mainnet with testing, a code audit and a permissions review. Talk to us.
Learn more: What Is Blockchain and How Does It Work? Types, Real Examples and Limits
Explained simply
Mainnet is the "real" blockchain: the network where tokens have value and there is no undo button. If you send crypto to the wrong address or deploy a contract with a bug, it usually cannot be reversed. Before getting here, projects are tested on a testnet, a copy of the network with worthless tokens.
Mainnet: key points
- A blockchain's main, production network, with real economic value
- Ethereum's has run since July 30, 2015, and on proof of stake since September 15, 2022
- On Ethereum it is identified by chain ID 1
- Every transaction pays gas: units used × (base fee + priority fee)
- Contracts are immutable by design: test and audit them before deploying
Mainnet: advantages
- Real value: tokens and transactions have economic effects
- Continuity: unlike a testnet, it is the production network and is not reset
- A live ecosystem: real wallets, explorers, oracles and stablecoins
Mainnet: disadvantages
- Real cost for every transaction in gas
- Irreversible mistakes: a deployed contract cannot be changed unless it is upgradeable
- More preparation: testing, auditing and secure key management
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