Faucet

A faucet is a website, app or bot that hands out small amounts of cryptocurrency for free, usually after a simple human check. Today the most common faucets dispense worthless test tokens on a testnet, so developers can pay transaction fees while they build and test software. The name comes from the image of coins dripping from a tap a little at a time.

Faucets began as a way to spread Bitcoin (BTC) when the coin had almost no market value, and a commercial version later appeared in which advertising-funded sites pay out tiny amounts of real coins. Faucets differ from an airdrop, where a project sends tokens to many addresses at once, and from a bounty, which rewards specific work. Their small, steady payouts also set them apart from crypto mining, which earns newly issued coins for securing the network.

Think of the free samples handed out at a supermarket. The shop is not trying to feed anyone; it wants people to try the product. Each shopper gets a small cup, and staff watch to stop the same person coming back twenty times.

A crypto faucet is that tasting stand. Early on, the free sample was real bitcoin, given away so that people would install a wallet and try sending a payment. Today most faucets give out play money for practice networks, where builders test their programs before they risk real funds. In both cases the operator limits how much each visitor can take, because otherwise one greedy person would drain the jar.

In 2010, software developer Gavin Andresen, who went on to lead Bitcoin's core development after Satoshi Nakamoto stepped back, launched a site called the Bitcoin Faucet. It gave 5 BTC to each visitor who solved a CAPTCHA and entered a wallet address, with Andresen funding it himself and accepting donations to keep it running. At the time, bitcoin was traded for fractions of a cent, so the giveaway was a cheap way to get the software into new hands.

Andresen soon had to deal with abuse, limiting payouts by IP address after some users found ways to claim repeatedly, and he wrote publicly about the difficulty of stopping people from gaming it. The faucet is now often quoted as an illustration of how cheap bitcoin once was, since coins given away for a CAPTCHA later became worth far more.

Public blockchains run separate test networks that copy the rules of the mainnet but use coins with no value. Developers still need these coins to pay each network's gas fee when they deploy a smart contract (SC) or send test transactions, and faucets are the usual way to get them. Ethereum's documentation lists faucets for its current testnets, many run by infrastructure providers, wallet companies and client teams. Bitcoin's testnet and signet have their own faucets, and other networks, including Solana (SOL), offer faucets or command-line tools that request test tokens.

Because test tokens are free, people sometimes hoard or resell them, which starves genuine developers. Operators therefore use controls such as:

• Human checks. CAPTCHAs and short waiting periods between claims limit automated requests.
• Identity links. Some faucets require a login through a developer account or social media profile.
• Mainnet balance checks. Some require the requesting address to hold a small amount of real coins on mainnet, which makes mass account creation costly.
• Proof-of-work faucets. Some ask the visitor's browser to perform a computing task, similar in spirit to proof of work (PoW), before paying out.

When a testnet is retired, its faucets close, and developers move to the replacement network.

A second type of faucet pays small amounts of real cryptocurrency, often measured in satoshis, in exchange for viewing adverts, solving puzzles or playing games. The site earns more from advertising than it pays out. Because the amounts are tiny, many such sites batch payouts through an intermediary account to avoid paying a transaction fee on every claim, a model related to microtransactions on the Lightning Network.

These faucets typically pay very little for the time spent. The format has also been used by fraudulent sites that ask for a deposit to "unlock" earnings, push malware, or request a seed phrase. No genuine faucet needs a seed phrase or a payment from the user, a point stressed in guides to identifying cryptocurrency scams.

For developers, faucets are part of normal tooling. A typical workflow is to create a test crypto wallet, request tokens from a faucet, deploy and test contracts on the testnet, and only then move to mainnet. Local development chains can create test balances directly, so public faucets are mainly needed for shared testnets where several teams, wallets and blockchain oracles interact. Wallet providers, node services and blockchain foundations often run faucets as a service to attract developers to their platforms.

• Ethereum.org: Networks (testnets and faucets)