RTB (real-time bidding)
Real-time bidding auctions each ad impression individually while the page loads, so buyers can price every impression on its own signals.
How it works
Without RTB, inventory is sold in advance, in fixed packages. With RTB, each time a page or app requests an ad, the request is described to the bidders: country, device, operating system, site category and similar signals. Each bidder decides within milliseconds whether to bid and how much, the highest valid bid wins, and the ad is served, all before the page finishes loading.
The buyer's advantage is precision: you can pay more for impressions your data says will convert and skip the rest. The cost is complexity, since bids, budgets and pacing have to be set up to run automatically.
Example
Three campaigns compete for one impression. A bids a $1.80 CPM. B bids $0.15 per click and has an expected CTR of 1%, so its eCPM = 0.15 × 0.01 × 1000 = $1.50. C bids a $1.20 CPM. A wins. In a second-price auction with a one-cent step, A pays $1.51 CPM instead of $1.80.
On UluMob
Every ad request on UluMob runs an auction among the campaigns targeting that zone, visitor and country. Eligible campaigns are ranked by eCPM: CPC, CPA and CPV bids are converted with an expected rate per format, so every pricing model competes on one scale. A fixed bid pays its bid. Smart CPM pays one cent above the next-highest bid, never more than your own bid and never below the publisher's reserve.