# Oracles

Oracles in æternity serve as trusted bridges between the blockchain and the outside world, enabling smart contracts to access external data. Unlike many blockchain platforms where oracles are implemented through complex smart contracts, æternity provides native protocol-level support for oracles, making them more efficient, cost-effective, and easier to use.

<table data-view="cards"><thead><tr><th></th><th data-hidden data-card-cover data-type="files"></th><th data-hidden data-card-target data-type="content-ref"></th></tr></thead><tbody><tr><td>Oracles Developer Documentation</td><td><a href="https://839505583-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FggVl0Jqy6Dd8f38hGk63%2Fuploads%2FU6AxxjQIzLuS9z4AwiGP%2F15deg-gradient.svg?alt=media&#x26;token=a2520256-1072-43f8-9a8d-3681276494bd">15deg-gradient.svg</a></td><td><a href="../../aeternity-developer-tools/protocol/core-protocol-components/oracles">oracles</a></td></tr></tbody></table>

### Understanding Oracles

Blockchains operate in closed systems, unable to directly access external information. An oracle solves this limitation by providing a mechanism to bring outside data onto the blockchain in a verifiable way. This could be anything from weather data and sports results to stock prices and supply chain information. What makes æternity's approach unique is that oracle functionality is built directly into the protocol rather than being implemented through smart contracts, leading to more efficient operation and reduced costs.

### æternity's Oracle Implementation

In æternity, oracles are first-class citizens of the blockchain, implemented through specific transaction types rather than smart contracts. This native integration means that common oracle operations like registration, querying, and response handling are streamlined and cost-effective. When an oracle is registered on the chain, it specifies the format it expects for both queries and responses, along with the fee required for each query.

The process begins with an oracle operator registering their service through a register oracle transaction. Once registered, any user can query the oracle using a query oracle transaction that includes the appropriate fee. Oracle operators monitor the blockchain for relevant queries and post oracle response transactions with answers in the predefined format. This makes the data available on-chain and accessible to any smart contract.

### Security and Reliability

æternity's oracle system includes several mechanisms to ensure reliability and prevent abuse. Oracle responses are permanently recorded on the blockchain, making them publicly verifiable and immutable. The system implements query TTL (Time To Live) parameters, which can be set as either absolute or relative key-block heights. This ensures that oracle queries receive timely responses and that users aren't charged for queries that go unanswered.

Oracles have specific lifetimes, defined in block height when they're registered. After this height, queries to the oracle no longer result in responses. However, oracle operators can extend their oracle's lifetime using an extend oracle transaction, providing flexibility while maintaining system integrity.

### Data Privacy and Cost Considerations

When using oracles, it's important to understand that any data posted to the blockchain becomes public. While this transparency is often beneficial, it requires careful consideration when dealing with sensitive information. For instance, using an oracle to verify personal data might not be appropriate as the data would become permanently public once posted to the chain.

æternity's oracle system is designed with cost-effectiveness in mind. The fee structure is transparent and predictable, with oracle operators setting their query fees upfront. This allows users to make informed decisions about oracle usage based on their specific needs and budget constraints.

### Practical Applications

Oracles in æternity enable a wide range of practical applications. Supply chain systems can use oracles to bring verified transaction data on-chain, decentralized insurance platforms can access real-world event data, and prediction markets can obtain reliable outcome information. The native implementation makes it particularly efficient for applications requiring frequent access to external data.

Smart contracts can use oracle responses as triggers for specific actions, creating automated systems that react to real-world events. For example, a smart contract might automatically execute payments based on weather conditions reported by an oracle, or adjust terms based on market prices provided through oracle data.

### Related Topics and Resources

For developers interested in implementing oracles in their applications, comprehensive technical documentation and code examples are available in the Developer Tools section. This includes detailed information about oracle transactions, query formats, and best practices for oracle implementation. Users looking to interact with existing oracles can find practical guides in the User Guides section of this documentation.
