What is on-chain / off-chain?
On-chain activity is recorded in a blockchain transaction anyone can verify, while off-chain activity happens in a company's database or a payment channel and is not.
Not yet verifiedHow we verify
3 min read
In this entry
On-chain activity is recorded in a blockchain transaction anyone can verify, while off-chain activity happens in a company's database or a payment channel and is not.
Trades inside an exchange are off-chain until you withdraw, which is why an exchange balance is a claim rather than a coin. Nothing moves on any blockchain when you buy Bitcoin on a centralized venue. A row changes in the exchange's ledger, and the coin backing it, if the exchange holds it, sits in a pooled wallet that never records your name.
That distinction is the single most useful thing to understand about custody. It explains why an exchange can halt withdrawals, why balances can be frozen, and why a venue's failure is a bankruptcy claim rather than a wallet problem.
How it works
On-chain means a transaction was broadcast, included in a block, and is verifiable by anyone with an explorer. It carries a fee, takes as long as the network takes, and cannot be reversed by the venue that sent it.
Off-chain covers several different arrangements that share only the property of not touching a blockchain.
Exchange internal ledgers. Every trade, and every transfer between two accounts on the same venue, is a database write. It is instant, usually free, and reversible by the operator.
Payment channels. Two parties open a channel with one on-chain transaction, then exchange signed balance updates privately, settling on chain only at the end. Lightning works this way.
Layer-2 execution. A rollup executes off the base chain but publishes its data back to it, so the arrangement is off-chain for execution and on-chain for availability. This sits between the two categories rather than in either.
The trade-off is consistent across all of them: off-chain is faster and cheaper, on-chain is verifiable and final without trusting anyone.
Example
Illustrative comparison of the same $500 purchase held two ways.
| Property | Exchange balance (off-chain) | Own wallet (on-chain) |
|---|---|---|
| Verifiable by you | No, it is the venue's record | Yes, on any block explorer |
| Cost to move within the venue | Usually free and instant | A network fee per transaction |
| If the venue fails | An unsecured creditor claim | Unaffected |
| Who can freeze it | The exchange | Nobody, absent your keys |
Neither column is correct for everyone. The exchange column is convenient and appropriate for funds you are actively trading. The wallet column is what makes the holding yours.
Why it matters when you buy
Buying is off-chain. Owning, in the sense that survives a venue failure, requires an on-chain withdrawal. Deciding where a given amount sits is the real question, and it usually resolves by size and timeframe rather than by principle. Withdrawal costs by venue are compared at the fee comparison, and the trade-offs are set out at Self custody vs exchange custody.
Related terms
- custodial — who holds the keys off-chain
- self custody — moving the balance on-chain
- proof of reserves — the partial check on claims
- block explorer — how on-chain activity is verified
- payment channel — off-chain transfers between two parties
- settlement — when a claim becomes final
Questions
Is an off-chain trade a real trade?
Yes. It is legally binding under the exchange's terms and it changes what you own economically. What it does not do is move anything on a blockchain, so it is only as reliable as the venue.
Why are internal transfers free?
Because nothing is broadcast. The venue updates two rows in its own database, which costs it almost nothing, so it usually charges nothing.
Is layer 2 on-chain or off-chain?
Both, in different respects. Execution happens off the base chain, but transaction data is published back to it so anyone can reconstruct and challenge the result. That publishing is what distinguishes a rollup from an exchange ledger.