All terms
Whether something is recorded on the blockchain itself or stored somewhere else.
Onchain means the data or the action is recorded in the blockchain state, visible to everyone and permanent. Offchain means it happens somewhere else: a server, a database, a layer 2 before it settles, or a file store.
Most real applications mix the two, because putting everything onchain is prohibitively expensive. The interesting question is always which parts are onchain, because those are the parts nobody can quietly change.
An NFT ownership record is onchain. The image it points at is almost always offchain, which is why storage choice matters.
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More web3 terms
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