Although I've already researched a lot about how Oraclize works, there is still an issue which is not clear to me.

As far as I understand the execution of smart contracts is done on all verifying nodes. Since Oraclize has to query some data from a public API and if thousands of nodes would perform such an action this may result in a DOS attack or is Oraclize off-chain and not realized as a smart contract?

I'll appreciate any explanation!

1 Answer 1


Oraclize is off-chain: They see a request and send a single web request, then send a transaction with the result to the network from their own address. Thousands of nodes verify that the transaction was really sent from their address. You have to trust that whoever controls that address will really send your contract the data they get from the website, because the nodes can't verify this. (This may change in future.)


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