> For the complete documentation index, see [llms.txt](https://docs.usdd.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.usdd.io/developers/core-contracts/median.md).

# Median

### **Purpose**

It provides the protocol’s trusted reference price.

### Key Responsibilities

* Maintains a whitelist of price feed contracts which are authorized to post price updates.
* Computes and updates the stored value when a new list of prices is received.

### Key Methods

* `poke()`\
  Updates price from whitelisted providers.
* `peek(what, data) / file(what, ilk, data)`\
  Get the price and validity.