On-chain means recorded on the blockchain being discussed. Always name the network: a record can be on Bitcoin, Ethereum or another specific chain.
What can be on-chain
A Bitcoin blockchain is an ordered, timestamped public ledger of transactions. On Ethereum, a signed transaction can update the network’s state once it is included in a validated block. These are examples of on-chain records.
An on-chain entry may be a transaction, a state change, or a reference such as a hash. It is not necessarily a complete copy of the file, event or item that it refers to.
The limits of an on-chain record
Recording something on a blockchain does not, by itself, prove a person’s identity, control of a key, ownership, legal rights, authenticity, privacy, safety or value. A blockchain can record data under its own rules; external claims need their own evidence.
Ethereum documentation makes a similar distinction for oracle data: making off-chain data available to a smart contract does not solve separate questions about that data’s correctness or availability.
On-chain and off-chain
On-chain means in the records or state of the named blockchain. Off-chain means outside it. The two can connect, but the words alone do not guarantee how or whether that connection works.
Sources
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