# External Pricing Source Configuration¶

By default, Hummingbot uses the market orderbook mid price (between the top bid and the top ask) as a starting price to calculate maker order prices. With external pricing sources, you can now use external sources for the starting mid price such as an external exchange or a custom API.

In a situation where the calculation of maker order prices from external sources would result in the order matching any existing orders on the order book, such order will be ignored. For example, if ETH-USDC market is currently displaying 109 bid and 111 ask. A specified external exchange is showing 99 bid and 101 ask on its book (mid price = 100). 2 maker orders will be proposed, a bid maker order at 98 (for 2% bid spread) and an ask maker order at 102 (for 2% ask spread). The 102 ask order will be ignored (as it would match the 109 bid order), only the bid order will be submitted to the exchange.

## Relevant Parameters¶

Parameter Prompt Definition
price_source_enabled Would you like to use an external pricing source for mid-market price? (Yes/No) When enabled, allows users to use an external pricing source for the mid price.
price_source_type Which type of external price source to use? (exchange/custom_api) The type of external pricing source.
price_source_exchange Enter external price source exchange name Name of exchange to be used for external pricing source.
price_source_market Enter the token pair on [price_source_exchange] The trading pair for the price source exchange.
price_source_custom Enter pricing API URL An external API that returns price.