# Chainlink Data Feeds Source: https://docs.chain.link/data-feeds > **NOTE: Talk to an expert** > > Contact us to talk to an expert about integrating Chainlink > Data Feeds with your applications. Chainlink Data Feeds are the quickest way to connect your smart contracts to real-world data such as asset prices, reserve balances, and L2 sequencer health. If you already started a project and need to integrate Chainlink, you can [add Chainlink to your existing project](/resources/create-a-chainlinked-project?parent=dataFeeds#installing-into-existing-projects) with the [`@chainlink/contracts` NPM package](https://www.npmjs.com/package/@chainlink/contracts). ## Types of data feeds Data feeds provide many different types of data for your applications. - [Price Feeds](#price-feeds) - [SmartData Feeds](#smartdata-feeds) - [Multiple-Variable Response (MVR) Feeds](#multiple-variable-response-mvr-feeds) - [Smart Value Recapture (SVR) Feeds](#smart-value-recapture-svr-feeds) - [Rate and Volatility Feeds](#rate-and-volatility-feeds) - [L2 sequencer uptime feeds](#l2-sequencer-uptime-feeds) - [Self-managed feeds](#self-managed-feeds) ### Price Feeds Smart contracts often act in real-time on data such as prices of assets. This is especially true in [DeFi](https://chain.link/use-cases/defi). For example, lending and borrowing platforms like [Aave](https://aave.com) utilize Data Feeds to assess collateral value accurately, while perpetual platforms such as [GMX](https://gmx.io) rely on these feeds to validate offchain data and ensure that each deposit or withdrawal executes at the correct market value. Data Feeds aggregate many data sources and publish them onchain using a combination of the [Decentralized Data Model](/architecture-overview/architecture-decentralized-model?parent=dataFeeds) and [Offchain Reporting](/architecture-overview/off-chain-reporting?parent=dataFeeds). - To learn how to use Price Feeds, see the [Price Feeds](/data-feeds/price-feeds) documentation. - See the [Data Feeds Contract Addresses](/data-feeds/price-feeds/addresses) page for a list of available networks and addresses. ### SmartData Feeds Chainlink SmartData is a suite of onchain data offerings designed to unlock the utility, accessibility, and reliability of tokenized real-world assets (RWAs). By providing secure minting assurances alongside essential real-world data such as reserves, Net Asset Value (NAV), and Assets Under Management (AUM) data, the SmartData suite embeds security and enriches data into tokenized RWA offerings. - To learn more about the broader SmartData suite, see the [SmartData](/data-feeds/smartdata) documentation. - See the [SmartData Contract Addresses](/data-feeds/smartdata/addresses) page for a list of available networks and addresses. #### Multiple-Variable Response (MVR) Feeds The SmartData suite includes [Multiple-Variable Response (MVR) Feeds](/data-feeds/mvr-feeds), which bundle multiple data points of various types into a single onchain update. Unlike traditional feeds that provide only one numeric value, MVR feeds can return multiple values of different types (both numeric and non-numeric) in a single transaction. - To learn more about MVR Feeds, see the [Multiple-Variable Response (MVR) Feeds](/data-feeds/mvr-feeds) documentation. - See the [SmartData Contract Addresses](/data-feeds/smartdata/addresses) page for a list of available networks and addresses. Use the *Show Multiple-Variable Response (MVR) feeds* checkbox to filter the list. ### Smart Value Recapture (SVR) Feeds Smart Value Recapture (SVR) Feeds introduce a mechanism to recapture Oracle Extractable Value (OEV), a form of MEV associated with oracle updates, often observed during liquidations. - To learn more, see the [Smart Value Recapture (SVR) Feeds](/data-feeds/svr-feeds) documentation. - Find SVR-enabled addresses on the [Price Feed Addresses](/data-feeds/price-feeds/addresses) page by filtering for SVR feeds. ### Rate and Volatility Feeds Several feeds provide interest rate curve data, APY data, and realized asset price volatility. - To learn more, see the [Rate and Volatility Feeds](/data-feeds/rates-feeds) documentation. - See the [Rate and Volatility Contract Addresses](/data-feeds/rates-feeds/addresses) page for a list of available networks and addresses. ### L2 sequencer uptime feeds L2 sequencer feeds track the last known status of the sequencer on an L2 network at a given point in time. This helps you prevent mass liquidations by providing a grace period to allow customers to react to these events. To learn how to use L2 sequencer uptime feeds, see the [L2 Sequencer Uptime Feeds](/data-feeds/l2-sequencer-feeds) documentation. ### Self-managed feeds Some networks publish Data Feed–style proxy contracts where **onchain updates are written by the chain or a third-party operator** (for example using a CRE workflow that reads [Chainlink Data Streams](/data-streams)), rather than through Chainlink Labs–managed decentralized oracle networks. **Chainlink Labs does not operate, monitor, or list addresses** for these deployments in official feed catalogs. For responsibilities, monitoring scope, and how to obtain contract addresses, see [Self-Managed Feeds](/data-feeds/self-managed-feeds). ## Components of a data feed Data Feeds are examples of decentralized oracle networks with different interfaces depending on the type of data they provide. Each feed type includes specific components: ### Single-value Feed Components Data feeds that deliver a single numeric value (such as price feeds or single-value [SmartData feeds](/data-feeds/smartdata)) include the following components: - **Consumer**: A consumer is an onchain or offchain application that uses Data Feeds. Consumer contracts use the [`AggregatorV3Interface`](https://github.com/smartcontractkit/chainlink/blob/contracts-v1.3.0/contracts/src/v0.8/shared/interfaces/AggregatorV3Interface.sol) to call functions on the proxy contract and retrieve information from the aggregator contract. For a complete list of functions available in the `AggregatorV3Interface`, see the [Data Feeds API Reference](/data-feeds/api-reference/#aggregatorv3interface). - **Proxy contract**: Proxy contracts are onchain proxies that point to the aggregator for a particular data feed. Using proxies enables the underlying aggregator to be upgraded without any service interruption to consuming contracts. Proxy contracts can vary from one data feed to another, but the [`EACAggregatorProxy.sol` contract](https://github.com/smartcontractkit/chainlink/blob/contracts-v1.0.0/contracts/src/v0.6/EACAggregatorProxy.sol) on Github is a common example. - **Aggregator contract**: An aggregator is a contract that receives periodic data updates from the oracle network. Aggregators store aggregated data onchain so that consumers can retrieve it and act upon it within the same transaction. For a complete list of functions and variables available on most aggregator contracts, see the [Data Feeds API Reference](/data-feeds/api-reference/#accesscontrolledoffchainaggregator). To learn how to create a consumer contract that uses an existing price feed, read the [Using Data Feeds](/data-feeds/price-feeds) documentation. ### MVR Feed Components [Multiple-Variable Response (MVR) Feeds](/data-feeds/mvr-feeds), which deliver multiple data points of various types in a single bundle, include the following components: - **Consumer**: A consumer is an onchain or offchain application that uses MVR Feeds. Consumer contracts use the [`IBundleAggregatorProxy`](/data-feeds/mvr-feeds/api-reference/#ibundleaggregatorproxy) interface to call functions on the proxy contract and retrieve bundle data. - **Bundle Aggregator Proxy**: This proxy contract points to the underlying bundle aggregator. Using proxies enables the underlying aggregator to be upgraded without service interruption to consuming contracts. The proxy exposes functions like [`latestBundle()`](/data-feeds/mvr-feeds/api-reference/#latestbundle), [`bundleDecimals()`](/data-feeds/mvr-feeds/api-reference/#bundledecimals), and [`latestBundleTimestamp()`](/data-feeds/mvr-feeds/api-reference/#latestbundletimestamp) for consumers to access the bundled data. To learn how to create a consumer contract that uses an existing MVR feed, read the [Using MVR Feeds on EVM Chains (Solidity)](/data-feeds/mvr-feeds/guides/evm-solidity) guide. ## Reading proxy and aggregator configurations Because the proxy and aggregator contracts are all onchain, you can see the current configuration by reading the variables through an [ABI](https://docs.soliditylang.org/en/latest/abi-spec.html) or using a blockchain explorer for your network. For example, you can see the [BTC/USD proxy configuration](https://etherscan.io/address/0xF4030086522a5bEEa4988F8cA5B36dbC97BeE88c#readContract) on the Ethereum network using Etherscan. If you read the BTC/USD proxy configuration, you can query all of the functions and variables that are publicly accessible for that contract including the `aggregator` address, `latestRoundData()` function, `latestAnswer` variable, `owner` address, `latestTimestamp` variable, and several others. To see descriptions for the proxy contract variables and functions, see the source code for your specific data feed on [Etherscan](https://etherscan.io/address/0xF4030086522a5bEEa4988F8cA5B36dbC97BeE88c#code#L568). The proxy contract points to an aggregator. This allows you to retrieve data through the proxy even if the aggregator is upgraded. If you view the `aggregator` address defined in the proxy configuration, you can see the aggregator and its configuration. For example, see the [BTC/USD aggregator contract](https://etherscan.io/address/0xF4030086522a5bEEa4988F8cA5B36dbC97BeE88c#code) in Etherscan. This contract includes several variables and functions, including another `latestRoundData()`. To see descriptions for the aggregator variables and functions, see the source code on [GitHub](https://github.com/smartcontractkit/libocr/blob/master/contract/AccessControlledOffchainAggregator.sol) or [Etherscan](https://etherscan.io/address/0xAe74faA92cB67A95ebCAB07358bC222e33A34dA7#code#F1#L1). You can call the `latestRoundData()` function directly on the aggregator, but it is a best practice to use the proxy instead so that changes to the aggregator do not affect your application. Similar to the proxy contract, the aggregator contract has a `latestAnswer` variable, `owner` address, `latestTimestamp` variable, and several others. ## Components of an aggregator The aggregator contract has several variables and functions that might be useful for your application. Although aggregator contracts are similar for each data feed, some aggregators have different variables. Use the `typeAndVersion()` function on the aggregator to identify what type of aggregator it is and what version it is running. Always check the contract source code and configuration to understand how specific data feeds operate. For example, the [aggregator contract for BTC/USD on Arbitrum](https://arbiscan.io/address/0x942d00008D658dbB40745BBEc89A93c253f9B882#code) is different from the aggregators on other networks. For examples of the contracts that are typically used in aggregator deployments, see the [libocr repository](https://github.com/smartcontractkit/libocr/blob/master/contract/) on GitHub. For a complete list of functions and variables available on most aggregator contracts, see the [Data Feeds API Reference](/data-feeds/api-reference/#accesscontrolledoffchainaggregator). ## Updates to proxy and aggregator contracts To accommodate the dynamic nature of offchain environments, Chainlink Data Feeds are updated from time to time to add new features and capabilities as well as respond to externalities such as token migrations, protocol rebrands, extreme market events, and upstream issues with data or node operations. These updates include changes to the aggregator configuration or a complete replacement of the aggregator that the proxy uses. If you consume data feeds through the proxy, your applications can continue to operate during these changes. Proxy and aggregator contracts all have an `owner` address that has permission to change variables and functions. For example, if you read the [BTC/USD proxy contract](https://etherscan.io/address/0xF4030086522a5bEEa4988F8cA5B36dbC97BeE88c#readContract) in Etherscan, you can see the `owner` address. This address is a [multi-signature safe](https://docs.safe.global/getting-started/readme) (multisig) that you can also inspect. If you [view the multisig contract](https://etherscan.io/address/0x21f73D42Eb58Ba49dDB685dc29D3bF5c0f0373CA#readProxyContract) in Etherscan using the *Read as Proxy* feature, you can see the full details of the multisig including the list of addresses that can sign and the number of signers required for the multisig to approve actions on any contracts that it owns. The multisig-coordinated upgradability of Chainlink Data Feeds involves time-tested processes that balance collusion-resistance with the flexibility required to implement improvements and swiftly react to external conditions. The approach taken to upgradability will continue to evolve over time to meet user requirements. ## Monitoring data feeds When you build applications and protocols that depend on data feeds, include monitoring and safeguards to protect against the negative impact of extreme market events, possible malicious activity on third-party venues or contracts, potential delays, and outages. Create your own monitoring alerts based on deviations in the answers that data feeds provide. This will notify you when potential issues occur so you can respond to them. ### Check the latest answer against reasonable limits The data feed aggregator includes both [`minAnswer` and `maxAnswer` values](https://github.com/smartcontractkit/libocr/blob/9e4afd8896f365b964bdf769ca28f373a3fb0300/contract/AccessControlledOffchainAggregator.sol#L33). On most data feeds, these values are no longer used and they do not stop your application from reading the most recent answer. For monitoring purposes, you must decide what limits are acceptable for your application. Configure your application to detect when the reported answer is close to reaching reasonable minimum and maximum limits so it can alert you to potential market events. Separately, configure your application to detect and respond to extreme price volatility or prices that are outside of your acceptable limits. ### Check the timestamp of the latest answer Chainlink Data Feeds do not provide streaming data. Rather, the aggregator updates its `latestAnswer` when the value deviates beyond a specified threshold or when the heartbeat idle time has passed. You can find the heartbeat and deviation values for each data feed at [data.chain.link](https://data.chain.link/) or in the [Contract Addresses](/data-feeds/price-feeds/addresses) lists. Your application should track the `latestTimestamp` variable or use the `updatedAt` value from the `latestRoundData()` function to make sure that the latest answer is recent enough for your application to use it. If your application detects that the reported answer is not updated within the heartbeat or within time limits that you determine are acceptable for your application, pause operation or switch to an alternate operation mode while identifying the cause of the delay. When the node detects that the heartbeat is reached, it initiates the latest round. Depending on congestion and network conditions, there may be a slight delay for the latest round to get onchain. During periods of low volatility, the heartbeat triggers updates to the latest answer. Some heartbeats are configured to last several hours, so your application should check the timestamp and verify that the latest answer is recent enough for your application. Users should build applications with the understanding that data feeds for wrapped or liquid staking assets might have different heartbeat and deviation thresholds than that of the underlying asset. Heartbeat and deviation thresholds can also differ for the same asset across different blockchains. Combining data from multiple feeds, even those with a common denominator, might result in a margin of error that users must account for in their risk mitigation practices. To learn more about the heartbeat and deviation threshold, read the [Decentralized Data Model](/architecture-overview/architecture-decentralized-model?parent=dataFeeds#aggregator) page.