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> **Documentation Index:** Fetch the complete configuration index at https://yandex.ru/dev/rtb/doc/en/llms.txt?revision=r20886070

# Introduction

Online advertising is a popular way to promote products and services. Site owners are ready to display ads, and advertisers are willing to buy ad space.

However, with so many sites and advertisers out there, searching for counterparties and signing direct contracts takes too much time and drives up costs. Both parties need an intermediary that places ads on sites using automated tools and ensures a fair pricing system. That's where the RTB host comes in, serving as a core component of the Yandex advertising ecosystem.

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The [OpenRTB](https://iabtechlab.com/standards/openrtb/) specification covers the technical details of RTB (real-time bidding) and provides guidelines for communication between advertisers, sites, and intermediaries.

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The RTB host runs an auction where advertisers compete to serve ads on their target sites. The advertiser with the highest bid wins, provided it meets the site owner's minimum price.

The RTB host acts as a price-setting tool based on classic market principles. Because auctions run automatically with high frequency (thousands of times a second), you can trust that the final price is fair.

## Purpose of this document

This document describes the RTB host application programming interface (API). Advertisers use this API to participate in auctions.

These auctions are fully automated, meaning automated systems operate on behalf of both advertisers and site owners. This document is intended for developers building automated systems on the advertiser side (demand-side platforms, or DSPs) and the publisher side (supply-side platforms, or SSPs).