# Oracle

Also written price oracle, oracle price.

*https://cryptomarkets.tools/glossary/oracle · next to On-chain Analytics Platforms*

**Definition:** A mechanism that puts an outside price where a contract or a matching engine can read it. On a chain it is a feed such as Chainlink or Pyth, written on-chain on a threshold, a heartbeat or a user's request. On a perpetuals venue it is the venue's own reference price, a median of other exchanges' spot prices. Both are reported values with a timestamp, never a live market.

This catalogue uses "oracle" in two senses, and the corpus needs both. A lending protocol liquidates
against one, and a perpetuals venue computes funding against another. They share a name and a
property: each is a number somebody reported, at a time somebody chose.

## How it works

**On a chain, a price has to be written before it can be read.** A smart contract cannot fetch a web
page. It reads storage, so somebody has to put a price there in a transaction, and the design
question is who does it and when.

- **Push.** Chainlink's data feeds update their answer "when the value deviates beyond a specified
  threshold or when the heartbeat idle time has passed". Between those events the on-chain value is
  the last one written, which can sit anywhere inside the threshold from the market. Chainlink tells
  consumers to check the `updatedAt` value returned by `latestRoundData()`, and to "pause operation
  or switch to an alternate operation mode" when it is older than the application can tolerate.
- **Pull.** Pyth publishes prices off-chain every 400 milliseconds and lets "anyone" post an update
  on-chain. Applications "need to update the on-chain price before reading it"; until somebody does,
  the stored value is whatever was last posted. Pyth characterises push oracles as typically updating
  every 10 minutes to an hour, which is a competitor's description and should be read as one.
- **The pool itself.** A DEX pool's price is readable on-chain with no feed at all, and it can be
  moved within one block by whoever orders the transactions. That is why contracts read a
  time-weighted average instead; [getting a DEX pair price](https://cryptomarkets.tools/how-to/get-a-dex-pair-price) covers
  it.

**On a perpetuals venue, the oracle is an internal reference.** Hyperliquid's validators publish a
spot oracle price for each perpetual every three seconds, computed as a weighted median of spot mid
prices on Binance, OKX, Bybit, Kraken, KuCoin, Gate, MEXC and Hyperliquid, weighted 3, 2, 2, 1, 1,
1, 1, 1. The price the clearinghouse uses is then a stake-weighted median of the validators'
submissions. It sets funding and is one input to the mark price. On dYdX each validator runs a
sidecar pulling prices from oracle providers and exchanges, the block proposer aggregates what they
submit, and the result checks collateral, triggers liquidations and fires stop-limit and
take-profit orders.

## Why it matters here

**An oracle price is not any one exchange's price.** A funding payment on Hyperliquid or a
liquidation on dYdX was computed against a median of several venues, filtered through validators.
Checking it against one exchange's chart finds a gap that is the method, not an error. The
[funding rate](https://cryptomarkets.tools/glossary/funding-rate) and [mark price](https://cryptomarkets.tools/glossary/mark-price) entries follow the
same number into the two calculations it feeds. The [Hyperliquid SDK](https://cryptomarkets.tools/tools/hyperliquid-python-sdk)
and the [dYdX clients](https://cryptomarkets.tools/tools/dydx-v4-clients) are where a program reads these values rather than
recomputing them.

**The timestamp matters more than the value.** A push feed's history is a series of updates that
happened when the price moved far enough or the heartbeat expired. It is irregular by design: a
quiet hour produces one row and a volatile minute produces several. Read it as a step function, the
value a contract would have been given until the next write, and not as a sample of the market
taken at regular intervals. A pull feed's on-chain history is worse as a price record, because it
contains only the moments somebody paid to update it. Anything built from oracle events pulled
through an on-chain SQL tool inherits that shape; [querying a chain with SQL](https://cryptomarkets.tools/how-to/query-a-chain-with-sql)
covers the tooling.

**Lending liquidations answer to the oracle, not the tape.** A position on a lending protocol is
closed when the protocol's oracle says it is under-collateralised, whatever an exchange chart showed
at that moment. A [liquidation](https://cryptomarkets.tools/glossary/liquidation) record from a lending market and one from a
perpetuals venue are two mechanisms, and [watching liquidations](https://cryptomarkets.tools/how-to/watch-liquidations)
keeps them apart.

**What an oracle secures is a measure of dependency, not accuracy.**
[DefiLlama](https://cryptomarkets.tools/tools/defillama) publishes total value secured per oracle, defined as the sum of the TVL
of every protocol that depends on it, and framed as the potential loss "if that oracle malfunctioned
or reported incorrect data". A large figure says many protocols trust the feed. It says nothing about
how close to the market the feed has been.

**Off-hours, the oracle decides what price means.** Assets whose underlying market closes — tokenized
stocks, stock-tagged perpetuals — are priced through oracles that must choose between a stale value,
a carried-forward one and a model. [Aster's card](https://cryptomarkets.tools/tools/aster-api) records that its stock
perpetuals are priced off an index built partly from the Pyth oracle and smoothed off-hours, and
[what a tokenized stock is](https://cryptomarkets.tools/guides/what-a-tokenized-stock-is) compares what Chainlink and Pyth
publish when the exchange is shut.

## Where you will meet this

- [DefiLlama](https://cryptomarkets.tools/tools/defillama.md)
- [Hyperliquid Python SDK](https://cryptomarkets.tools/tools/hyperliquid-python-sdk.md)
- [dYdX v4 Clients](https://cryptomarkets.tools/tools/dydx-v4-clients.md)
- [Aster Market Data API](https://cryptomarkets.tools/tools/aster-api.md)

## Sources

1. [Data Feeds — deviation threshold, heartbeat and checking updatedAt](https://docs.chain.link/data-feeds) — Chainlink, read 2026-09-27
2. [Pull updates — pull and push oracles compared](https://docs.pyth.network/price-feeds/core/pull-updates) — Pyth Network, read 2026-09-27
3. [Oracle](https://hyperliquid.gitbook.io/hyperliquid-docs/hypercore/oracle) — Hyperliquid, read 2026-09-27
4. [Oracle Prices](https://docs.dydx.xyz/concepts/trading/oracle) — dYdX, read 2026-09-27
5. [Data Definitions — Total Value Secured (TVS, for oracles)](https://docs.llama.fi/analysts/data-definitions) — DefiLlama, read 2026-09-27

*Last updated 2026-09-27. A reference page, corrected in place — not a dated post.*