In digital advertising, two similar-sounding terms—bid request and ad request—play important but very different roles. If you're working in programmatic advertising or running campaigns on the open web, mobile apps, or connected TV platforms, it's helpful to understand what each one means and how they fit into the ad delivery process.
What Is a Bid Request?
A bid request is sent from a publisher’s supply-side platform (SSP) or ad exchange to potential advertisers and DSPs. It happens during the real-time bidding process and represents an opportunity for a brand to bid on a single impression. Each bid request includes data about the available ad space and the user who might see the ad.
This data can include:
- Ad unit size (e.g., 300x250 or 15-second video)
- Page URL or app name
- User location (city, state, ZIP)
- Device type and browser
- Demographic segments (if available)
- Contextual info like content category or keywords
- Price floor (minimum bid set by the publisher)
The DSP’s bidder reviews each bid request and decides if it wants to submit a bid. If it does, the bid includes the amount the advertiser is willing to pay, along with which ad creative should be shown. The highest bid wins, and that ad is served to the user.
This entire process takes place in milliseconds and is repeated for every single impression across the open web, apps, and streaming platforms.
What Is an Ad Request?
An ad request happens earlier in the process. It comes directly from the user’s device—typically when someone visits a website or opens an app that has ad space. When this happens, the site or app sends a request to an ad server asking for an ad to be delivered.
The ad request includes:
- Information about the user (like location, browser, or app version)
- Details about the available ad slot (size, placement, and format)
- Page or screen context
- Any targeting parameters set by the publisher
The ad server then processes this information to determine which ad to show. This may involve selecting an ad directly from a campaign the publisher is running, or it may trigger a programmatic auction, which results in a bid request being sent to multiple DSPs.
So, while an ad request starts the process by asking for an ad, the bid request is what gets sent out during the auction to find the right ad based on bids from advertisers.
Why This Matters
If you're a brand, understanding the difference between ad and bid requests helps you track how your ads are being served. Bid requests help you understand the volume and type of inventory available for your campaign, while ad requests give insight into how often users are triggering opportunities for ads to be shown.
For publishers, managing ad requests efficiently is key to maximizing fill rates and revenue. For advertisers, filtering and responding to the right bid requests is critical for targeting the right users and hitting performance goals.
GEO-specific data is often included in both types of requests. This allows for location-based targeting, which is especially useful in campaigns that want to reach users in a specific market or region.
Sam Khoury
Founder, Cedar Consultants
Creative consulting solutions for Adtech