How OpenRTB Works — And Why It Still Powers Programmatic in 2025

Open Real-Time Bidding (OpenRTB) is the backbone of programmatic ads, enabling the automated buying and selling of digital ad impressions in real time. Developed by the IAB Tech Lab, it standardizes how demand-side platforms and supply-side platforms communicate, allowing programmatic ad auctions to take place in the split second it takes for a webpage or app to load.

Although it operates behind the scenes, OpenRTB is a central component of the modern digital ad ecosystem. It powers personalized ad delivery across a wide range of formats, including display, mobile, video, and connected TV.

The market built on this protocol is growing fast. Recent data estimates that the global real-time bidding market was worth nearly $19 billion in 2024 and is expected to climb past $90 billion by 2033. This rise is fueled by advancements in AI, greater digital ad spending, and a push for scalable and efficient targeting. North America currently leads the market, holding over 40 percent of the share.

What Is OpenRTB? A Quick Refresher

OpenRTB is a technical standard that enables different parts of the programmatic ecosystem, such as SSPs, DSPs, and ad exchanges, to communicate and transact in real time. It serves as a shared language that simplifies how ads are bought and sold almost instantly.

Before OpenRTB existed, each platform used its own method for handling real-time ad auctions. This created confusion, slowed down processes, and made integration between systems difficult. OpenRTB was created to solve these problems by standardizing how programmatic ad requests, responses, and bids are formatted and exchanged. As a result, auctions can now take place in just milliseconds when a user visits a website or opens an app.

The primary purpose behind OpenRTB was to improve the speed, transparency, and scalability of real-time bidding. It allows advertisers to deliver relevant advertising to users more effectively while helping publishers earn more from their available ad space. Since its introduction, the protocol has continued to evolve to support new media formats, such as video and connected TV.

How OpenRTB Actually Works

A quick, automatic auction that occurs each time a user visits a webpage or application is the core of OpenRTB. The diagram below illustrates this real-time process in a simplified form.

It all begins when a user visits a site. As the page loads, the publisher’s system sends a bid request through an SSP to the OpenRTB protocol. This request contains important, anonymized data, such as basic information about the user (like location and browser type), the device they are using, the type of content being viewed, and the available ad space (also called inventory). It may also include data on user behavior or past interactions to help advertisers decide if the user matches their target audience.

This bid request is shared with multiple DSPs and ad exchanges, which analyze the data and decide how much they are willing to pay to show an ad. Each one sends back a bid response, which includes their offer and the creative (the actual ad). OpenRTB then helps select the highest bid and returns the winning ad to be displayed, right as the page finishes loading.

All of this happens in just a few milliseconds. The user never notices, but behind the scenes, OpenRTB ensures the right ad is shown to the right person at the right time, maximizing value for both advertisers and publishers.

Key Components of an OpenRTB Transaction

Every OpenRTB transaction consists of three main components that work together to deliver the right ad in real time. 

• The process begins with a bid request sent by the SSP. This request contains crucial, anonymized data about the user, such as device type, location, browser, and contextual information about the page or app. It also includes details about the available ad space, including size, format, and placement.
• Next comes the bid response from DSPs. Based on the information in the bid request, each DSP evaluates the opportunity and sends back a response that includes a bid price and the creative asset they want to serve. This response must be fast and accurate to compete effectively in the auction.
• Finally, the win notification and ad serving phase occurs. The winning DSP is informed after the highest bid is chosen. The chosen ad is then served to the user almost instantly.

Throughout this process, transparency, speed, and precise data matching are essential to ensure the right ad is shown at the right moment, creating value for all parties involved.

Why OpenRTB Still Matters in 2025

OpenRTB remains a core standard in programmatic advertising due to its widespread adoption and strong support across the industry. It enables seamless communication between diverse platforms, making it easier for advertisers, publishers, and tech providers to integrate and transact at scale.

Its auction-based model ensures fair competition and price discovery, allowing advertisers to bid based on real value while helping publishers maximize revenue. The protocol also supports scalable operations, handling millions of transactions per second across global markets.

Perhaps most importantly, oRTB continues to evolve with the industry. It has expanded beyond traditional display to support formats like connected TV (CTV), native advertising, and audio. Ongoing updates by the IAB Tech Lab ensure the protocol stays relevant, flexible, and responsive to changing technologies and privacy standards. This adaptability keeps OpenRTB at the center of innovation in programmatic advertising, even as the ecosystem grows more complex.

BI oRTB integration

Why oRTB Still Deserves a Front Seat

OpenRTB continues to prove its value by offering a fast, transparent, and scalable way to power digital ad transactions. Its flexibility allows it to adapt to emerging formats and technologies, making it a future-proof solution in an evolving industry. As the standard continues to improve, it remains essential for efficient, data-driven advertising.

For Bidinfluence partners, integrating with OpenRTB means faster time to market, broader reach, and better monetization. It simplifies connections and supports growth across channels. Ready to explore the benefits? Get in touch with us through this form to learn more.