Blockchain Oracles

What is a blockchain oracle?

A blockchain oracle supplies externally sourced information for use by smart contracts. The information might be a market observation, a weather measurement or an event result. The oracle provides a connection between the external source and the onchain application; it does not make every claim infallible merely by publishing it.

Our use of the word also includes the broader idea of a queryable answer source. Keep that broad meaning separate from a specific blockchain integration. An answer can be an observation, a forecast or a resolved outcome, and each needs its own interpretation.

Follow the information, not just the interface

A useful review follows the source, collection method, report validation, delivery path and consuming contract. Ask which participant can change the value, which dependency can interrupt updates and which configuration determines the accepted feed. Then document what the application does when those assumptions fail.

Delivery models include maintained feeds, transaction-supplied updates and request-response workflows. Choose a model around your application's timing and evidence needs rather than assuming that one architecture is automatically appropriate for every use case.

Make the acceptance policy explicit

An application should identify the exact question, feed or asset, units, time window and required verification state before taking action. A valid report for the wrong asset is still the wrong input. A signed observation can still be too old for a new operation.

Separate correctness of delivery from correctness of the original observation. Source diversity, cryptographic checks and dispute mechanisms can address different problems, but their benefits depend on the actual implementation and assumptions. The reference notes identify the foundational documentation used in this guide.

Choose your next step

For contract-side decisions, continue to Smart Contract Oracles. For interfaces used outside a chain, explore Oracle API. For estimates about events that have not yet occurred, start with Prediction Oracles.

The blockchain oracle definition

For an additional overview of the blockchain meaning of oracle, read Wikipedia’s article. The broader forecasting meaning is covered separately in our prediction guides.

Blockchain oracle on Wikipedia