Blockchain Mainnet: Definition, Mainnet vs Testnet, Launches and Network Upgrades

What is a blockchain mainnet?

A mainnet (short for "main network") is the production version of a blockchain network. It is the live, lasting ledger that users, applications, validators or miners, and token holders actually use. Ethereum's developer documentation defines Mainnet as "the primary public Ethereum production blockchain, where actual-value transactions occur on the distributed ledger" [2]. Solana's documentation describes its mainnet as "a permissionless, persistent cluster for Solana users, builders, validators and token holders," where tokens are real SOL [6].

The idea rests on the general properties of blockchains. The U.S. National Institute of Standards and Technology (NIST) describes blockchains as "tamper evident and tamper resistant digital ledgers implemented in a distributed fashion," usually without a central authority, where published transactions cannot be changed under normal operation [1]. Because mainnet records are hard to reverse and its assets have market value, mistakes made on a mainnet, such as buggy smart contracts, wrong transfers or broken upgrades, have real financial consequences. That is the main reason separate test networks exist.

Where the mainnet sits in the release lifecycle

Most public blockchains send software through several network stages before it reaches production. The names and number of stages differ between projects, but the general order is local or development networks, then public testnets, then mainnet.

Stage	Typical purpose	Value of tokens	Examples
Local / private development network	Fast, isolated testing controlled by one developer or team	None	Bitcoin regtest, where blocks "can simply be mined on command" [7]; Ethereum development networks [2]
Devnet	Public sandbox for trying out a network	None; tokens come from a faucet	Solana Devnet [6]
Testnet	Testing releases, smart contracts and protocol upgrades "in a production-like environment before deployment to Mainnet"	Meant to have none	Ethereum Sepolia and Hoodi [2]; Solana Testnet [6]; Bitcoin testnet and signet [7]
Mainnet	Production use with real assets	Real economic value	Bitcoin, Ethereum and Solana mainnets [2][6][8]

Solana's documentation describes this order for software releases. Testnet usually runs the newest version, Devnet runs software closer to mainnet, and mainnet runs the most stable release branch [6].

Mainnet vs testnet: key differences

Aspect	Mainnet	Testnet
Asset value	Tokens have real value	Test tokens are meant to have no real value, though Ethereum's documentation notes that markets have appeared for some scarce testnet ETH [2]
How tokens are obtained	Bought, earned or transferred	Usually free from faucets [6]
Validator set	Open to participants under the protocol's rules on permissionless chains	Can be permissioned. For example, Sepolia's validators are controlled by client and testing teams [2], and Bitcoin signet blocks need signatures from authorized signers [7]
Lifespan	Meant to run indefinitely	Can be retired or reset. Ethereum's Ephemery testnet fully resets about every 28 days [2]
Cost of errors	Real financial loss is possible	No real financial loss

Testnets are not permanent

Testnets are replaced as needs change. After the Pectra upgrade was activated on testnets on 14 February 2025, Ethereum's Holešky testnet had long inactivity leaks and a validator exit queue estimated at about a year. The Ethereum Foundation then launched a new testnet, Hoodi, in March 2025 [3]. Holešky was later deprecated as of September 2025 [2]. The Foundation now points application developers to Sepolia and staking operators to Hoodi [5]. In March 2025 the Foundation projected end-of-life dates of 30 September 2026 for Sepolia and 30 September 2028 for Hoodi [3]. Developers should check current guidance, because these schedules can change.

How a mainnet launches

The genesis block

A mainnet usually starts with a genesis block, the first block of the chain, which does not reference any earlier block [8]. Bitcoin's genesis block is dated 3 January 2009. Its coinbase data includes the text "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks" [8]. Ethereum's first production release, Frontier, went live on 30 July 2015 after the Olympic test release. At the time, the release coordinator warned users not to "put a lot of value at risk" [9].

Token migrations ("mainnet swaps")

Some projects first issue tokens on an existing chain and move holders to their own mainnet later. EOS tokens, for example, first circulated as ERC-20 tokens on Ethereum. Holders had to register or swap before the EOS mainnet launch in June 2018, or their tokens would become "frozen and no longer transferable on the Ethereum network" . Migrations like this depend on each project's instructions and deadlines. Holders usually rely on official channels or exchanges to complete them.

Upgrading a mainnet

Mainnet rules can only change when many independent node operators run compatible software, so upgrades have to be coordinated. The usual pattern is to specify the change, activate it on testnets, and then schedule mainnet activation at a set block height or epoch.

Ethereum Pectra (2025): activated on the Sepolia, Holešky and Hoodi testnets first, then on mainnet on 7 May 2025 at epoch 364032. Node operators had to update both execution-layer and consensus-layer clients. Nodes that did not update would lose their connection to upgraded peers, and the network could split into incompatible subsets [4].
Ethereum's Merge (2022): the move to proof of stake was run on testnets such as Ropsten before being executed on mainnet on 15 September 2022. The Beacon Chain had been running alongside mainnet since 1 December 2020 [11].
Bitcoin Taproot (2021): a soft-fork upgrade specified mainly in BIP341. It activated at block height 709,632 in November 2021 after a "speedy trial" signalling process [12].

Chain IDs: keeping mainnet and testnets apart

Networks that share a codebase need a way to stop a transaction signed for one network from being valid on another. Ethereum's EIP-155, written by Vitalik Buterin and created on 14 October 2016, adds a chain identifier to transaction signatures. This allows transactions that work on Ethereum without working on Ethereum Classic or a testnet [10]. EIP-155 lists chain ID 1 for Ethereum mainnet, 3 for Ropsten, 4 for Rinkeby and 5 for Goerli, and 1337 as the default for Geth private chains [10]. Bitcoin Core separates its networks by mode and port. For example, testnet uses peer-to-peer port 18333, signet uses 38333 and regtest uses 18444 [7].

Practical guidance

Check the network before you sign. Wallets and developer tools can connect to several networks. Confirm the selected network or chain ID, because mainnet transfers move real assets.
Test on the right testnet. Ethereum recommends Sepolia for application development and Hoodi for validator and staking testing [2][5]. Bitcoin developers often combine regtest for automated local tests with public testnet or signet [7].
Don't treat testnet tokens as investments. They are meant to have no value [2], and testnets can be deprecated or reset.
Node operators: follow upgrade announcements. Running outdated client software after a scheduled upgrade can leave a node on an incompatible fork [4].
Use production infrastructure for production apps. Solana, for example, says its public RPC endpoints are not intended for production applications [6].

Limitations and common misconceptions

"Mainnet launch" is a technical milestone. It does not show that a project is secure, decentralized or financially sound. Early mainnets can be deliberately minimal: Ethereum's Frontier was a command-line release for developers [9]. The label "mainnet" also does not mean that software on it has been audited, and bugs found only after deployment can affect real assets. Finally, the terms devnet and testnet mean different things in different projects. Readers should check each network's own documentation.