Bid request

What is Bid request?

A bid request is a data packet automatically generated in real-time bidding (RTB) systems each time a user loads a web or app page containing an available ad slot. It transmits consented user and contextual data to advertisers, ad exchanges, and supply-side platforms so they can evaluate whether to place a bid. Bid requests are the foundational mechanism that makes programmatic advertising possible, enabling instantaneous auctions across thousands of ad impressions simultaneously.

How it works

When a user accesses a page with an open ad slot, the publisher's ad server or supply-side platform generates a bid request and broadcasts it across connected ad exchanges and demand-side platforms. The entire process completes within the time it takes a page to load, typically under 100 milliseconds.

Bid Request Generation

The bid request is triggered the moment an ad slot becomes available. The SSP packages available data about the user, device, and placement into a structured data object, typically following the OpenRTB specification, and sends it simultaneously to eligible buyers.

Data Transmitted in a Bid Request

Bid requests carry several categories of information that advertisers use to assess relevance and bid value.

• User demographics: Age, gender, and geographic location collected with user consent help advertisers match ads to defined audience segments.
• Browsing and in-app behavior: Past interactions and content engagement signals indicate user interests and intent.
• Device information: Device type, operating system, screen size, and connection type inform creative format selection and targeting eligibility.
• Contextual data: The URL or app bundle, content category, and placement details tell buyers what environment the ad will appear in.
• Cookies and identifiers: On web, cookies support user recognition and retargeting. On mobile, advertising identifiers such as GAID or IDFA serve a similar function, subject to user consent and privacy controls.
• Ad slot specifications: Dimensions, position on page, and format type allow buyers to determine whether their creative assets are compatible.

Auction and Delivery

After receiving a bid request, each eligible advertiser evaluates whether the user and placement match their campaign parameters. Those who choose to participate submit a bid response with a price. The highest qualifying bid wins the auction, and the winning ad is served to the user's device in real time. This entire cycle repeats at every new page load or app screen transition.

Why it matters

Bid requests are the engine of programmatic advertising. Without them, automated ad buying at scale is not possible. The quality and completeness of bid request data directly determines how accurately advertisers can reach their intended audiences. Richer data signals enable more precise targeting, more competitive auctions, and more relevant ad experiences for users.

For advertisers, bid requests determine which impressions they have the opportunity to compete for. Incomplete or low-quality bid request data leads to poor targeting matches, wasted spend, and lower return on ad spend. For publishers, well-structured bid requests attract more competitive bids, increasing fill rates and effective CPM.

Bid requests are also a key surface where privacy regulation intersects with programmatic advertising. Regulations such as GDPR and CCPA, along with consent management platforms, govern what user data can legally be included in a bid request. As identifiers like third-party cookies are phased out, the industry is adopting privacy-preserving alternatives that change what data bid requests can carry and how targeting is performed. Advertisers and publishers alike must monitor these shifts to maintain auction competitiveness and regulatory compliance.

How to interpret and optimize bid request data

Understanding bid request structure and data quality is essential for improving programmatic campaign performance.

1. Audit your bid request data completeness. Work with your SSP or ad server to verify that bid requests sent on your behalf include all available consented signals: user demographics, device data, contextual placement information, and valid advertising identifiers. Missing fields reduce buyer confidence and lower bid prices.

2. Align with OpenRTB standards. The OpenRTB specification, maintained by the IAB, defines the standard format for bid requests and responses. Ensuring your integration conforms to the current OpenRTB version maximizes compatibility with demand-side platforms and increases auction participation.

3. Implement a consent management platform (CMP). Bid requests must only include data for which the user has given valid consent. Integrating a CMP ensures that consent signals are passed correctly alongside bid request data, keeping your programmatic stack compliant with privacy regulations.

4. Monitor bid response rates. A low bid response rate relative to bid requests sent often signals data quality issues. Analyze which request fields are missing or malformed, and address them to improve auction competitiveness.

5. Adapt to identifier changes. As third-party cookies deprecate and mobile identifier availability is restricted through frameworks like Apple's ATT, ensure your bid requests incorporate privacy-preserving alternatives and contextual signals. Tools like Airbridge support mobile attribution measurement in identifier-limited environments, giving advertisers meaningful data even when traditional identifiers are unavailable.

6. Use targeting parameters effectively. On the buy side, configure your DSP to filter bid requests by the signals that matter most to your campaigns, such as device type, location, content category, and audience segment. Precise filtering reduces wasted bids and improves overall campaign efficiency.

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