The 100-millisecond auction
What happens between you opening a web page and an ad appearing: a real-time auction that finishes faster than a blink.
The 100-millisecond auction
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You open a page
Your browser starts loading an article. The page has a space for an ad, but nobody has decided which ad yet.
- You open a page: Your browser starts loading an article. The page has a space for an ad, but nobody has decided which ad yet.
- The slot goes up for sale: Code on the page (often Prebid) calls the publisher’s SSP: “I have a 300×250 slot, on this article, seen by this device, in Mumbai.” That message is a bid request.
- Is anyone real here?: Before the slot is offered, traffic checks look for signs of invalid traffic: known data-center IPs, bot user agents, spoofed domains. Suspicious requests are dropped here, pre-bid.
- Bid requests fan out: The SSP sends the bid request to many DSPs at once, each buying for different advertisers. Every DSP now has a few dozen milliseconds to decide.
- Bids come back: Each DSP checks its campaigns and data: is this someone our advertiser wants? What is this impression worth? It answers with a price, per thousand impressions (CPM).
- Highest bid wins: In today’s first-price auction the highest bid wins and pays what it bid. DSP A wins at $4.20 CPM, which is $0.0042 for this single impression.
- The ad is delivered: The winner’s ad server sends the creative (the image or video) to the page. Tracking pixels fire so the impression can be counted, billed and measured.
- You see an ad: All of that happened before the page finished loading. It repeats billions of times a day, which is why fraudsters target it: fake “visitors” can collect real bids.
Step by step
- You open a page (0 ms)Your browser starts loading an article. The page has a space for an ad, but nobody has decided which ad yet.
- The slot goes up for sale (5 ms)Code on the page (often Prebid) calls the publisher’s SSP: “I have a 300×250 slot, on this article, seen by this device, in Mumbai.” That message is a bid request.
- Is anyone real here? (12 ms)Before the slot is offered, traffic checks look for signs of invalid traffic: known data-center IPs, bot user agents, spoofed domains. Suspicious requests are dropped here, pre-bid.
- Bid requests fan out (20 ms)The SSP sends the bid request to many DSPs at once, each buying for different advertisers. Every DSP now has a few dozen milliseconds to decide.
- Bids come back (70 ms)Each DSP checks its campaigns and data: is this someone our advertiser wants? What is this impression worth? It answers with a price, per thousand impressions (CPM).
- Highest bid wins (85 ms)In today’s first-price auction the highest bid wins and pays what it bid. DSP A wins at $4.20 CPM, which is $0.0042 for this single impression.
- The ad is delivered (95 ms)The winner’s ad server sends the creative (the image or video) to the page. Tracking pixels fire so the impression can be counted, billed and measured.
- You see an ad (≈100 ms)All of that happened before the page finished loading. It repeats billions of times a day, which is why fraudsters target it: fake “visitors” can collect real bids.