Seed phrase

A seed phrase is the secret list of words that backs up a crypto wallet and can restore every account in it, so anyone who learns the phrase controls all of the wallet's funds. ethereum.org's security page calls the recovery phrase the master key to a wallet: anyone who has it can access all of your accounts and drain every asset, and no legitimate service, support agent or website will ever ask for it. It also advises against screenshots, which can sync to the cloud. Arbitrum's ARB airdrop page repeated the point: don't ever share your seed phrase.

Revoke.cash lists the common ways phrases leak: fake game launchers and other downloads carrying malware, phishing sites with "restore wallet" forms, copies saved in cloud storage, and terminal commands disguised as airdrop claim instructions shared in Discord or Telegram. Once a phrase is exposed there is no undo, and revoke.cash says the affected addresses have to be abandoned. No airdrop claim needs the phrase; see also private key and phishing.