Transactions or data that happen outside a blockchain. Instead of recording every move on the ledger, you settle matters peer-to-peer, then post the final state later. Fast, cheap, private—no miner sees your business until you want them to.
Why it matters for domain ops: you can pay for a domain registration off-chain (lightning network, direct crypto transfer, whatever), and the registrar settles on-chain when it suits them or not at all. Bunkerdomains accepts off-chain crypto by default—no blockchain clutter, no transaction trail for analytics firms. You get pseudonymity without the gas fees.
Common off-chain methods: payment channels (Lightning), sidechains, rollups, custodial escrow, or just a straight wallet-to-wallet handshake. The trade-off is trust. Off-chain = you're trusting the other party to honor the deal until it hits the ledger. That's why multisig wallets and reputable registrars matter.