The report is based on the Roxot Prebid Analytics data from publishers who agreed to participate in the research. Roxot Prebid Analytics collects client-side data about all header bidding auctions running in the website's prebid.js wrapper and all demand partners participating. Therefore, the report is based only on the client-side data.
We analyzed 2.2billion requests generated by European users (Germany, France, Spain, Italy, United Kingdom, Belgium, Netherlands, Finland, Sweden) on 102 websites from April 1st to June 20th, 2018.
Please, mind that the report is based ONLY on the Roxot Prebid Analytics users data and might be biased to some of the bidders. The users might have implemented demand partners incorrectly, which would affect the results of this report. However, we took measures to prevent any data inconsistency:
Reduced data contribution of the sites with total revenue share higher than 20%
Excluded sites with abnormal bidder behavior (e.g. 0 bids, bid rate lower than 5% or higher than 90%)
Combined data of different adapters for the same demand provider (e.g PulsePoint and PulsePoint Lite, AppNexus and AppNexus AST, etc.)
Excluded bidders with less than 10 million ad requests
Bidder Performance Analysis
The Adoption Rate shows how many ad requests a bidder received from the total number of requests on all sites participated in the research. If we had analyzed 100 auctions and a bidder had received 25 requests, its Adoption Rate would have been 25%.
This metric provides us with a context for future sections of the report. Comparing Bid Rates, Win Rates, and Efficiency, keep in mind how many requests a bidder analysis is based on.
Bid Rate shows how often a demand partner replies with a bid to an ad request. If there is no bid, demand partner might be too slow or not have ads for a particular website visitor. The bidding frequency directly affects the competition inside your wrapper and your total Fill Rate.
*Bid Rate - how often a bidder replies with a bid to an ad request
Bidder;Desktop Bid Rate (EU);Mobile Bid Rate (EU)
Index Exchange;51% ;24%
Top bidders by Win Rate*
The Win Rate shows how a bidder competes with other partners in the header. To get impressions and generate revenue a bidder has to both bid often and win often. A high Bid Rate would mean nothing if partner's bids never win.
*Win Rate - how often bidder's bids win prebid auctions
Bidder;Desktop Win Rate (EU);Mobile Win Rate (EU)
The slowest bidders
The "winners" in this category are the bidders who get timed out more often than others. If you are actively working on improving your page load times, pay the closest attention to this section. Timeout Rate* is a must-have metric when analyzing bidder's performance. It helps you identify adapters that damage your UX and optimization options.
*Timeout Rate - percentage of ad auctions that a bidder didn't provide a bid in the time specified in your prebid.js timeout settings.
Bidder Performance Comparison in the EU and the US
We use the data from the report above and the recent report for the US to compare bidder performance in the EU and the US. Despite these reports are based on different time periods, we made sure the data is reliable. The US report data varies by less than 5% when the time period is changed to April 1 - June 20, 2018.
Bid Rate Comparison | EU vs US
Bidders differently respond to European and North American ad requests. The difference in Bid Rate is more than 20% for 7 out of 14 bidders. For 4 out of 7 remaining bidders, the difference exceeds 10%.
9 SSPs bid for European mobile requests similarly to North American mobile requests. For only 6 out of 14 bidders, the difference exceeds 10%.
Bid Rate Comparison Conclusion
AppNexus is the most stable bidder. Its Bid Rates vary in 5% range which may be considered as noise.
Rubicon rarely bids for European inventory. Rubicon is the top bidding SSP on the US market with 68.4% Desktop Bid Rate. In Europe, the Desktop Bid Rate drops to 27%. However, Rubicon's Mobile Bid Rate is stable. The difference between the US Mobile Bid Rate and the EU Mobile Bid Rate is only 4% which may be considered as noise.
FAN bids on 45% of European Desktop ad requests. Its Bid Rate for the US Desktop demand is only 20%. This may indicate the difference in browsing behavior between European and North American Facebook users.
Win Rate Comparison | EU vs US
Bidders differently compete for European desktop inventory in comparison with North American inventory. For 8 out of 14 bidders, the difference in Win Rate exceeds 10%. For 4, the difference is more than 20%.
Win Rate differences have a similar pattern for both desktop and mobile requests. For 5 bidders, the difference in Mobile Win Rate exceeds 20%.
Win Rate Comparison Conclusion
FAN wins less header bidding auctions for European inventory than for North American inventory on both mobile and desktop. Its Win Rate in the EU is around 50%. In the US, FAN wins over 80% of auctions it participates in.
OpenX is more competitive in Europe. It's the top SSP in regards to Desktop Win Rate. OpenX wins 67% of auctions for European desktop inventory but only 25% of North American desktop requests. Mobile Win Rate is higher in the EU too - 38% vs 24% in the US.
Despite the dropped Bid Rate, Rubicon wins more auctions in Europe than in the US. That's especially true for mobile inventory. 64% Mobile Win Rate in the EU vs 30% in the US
Total Bidder Efficiency* & Comparison Conslusion
* Total efficiency — how many requests to a bidder resulted in its impressions (Bid Rate * Win Rate)
Conclusion Understanding your demand and mapping it to the appropriate bidders is key to crafting a successful mix of SSPs. If European users contribute a significant percentage of your total revenue, pay close attention to this report.
OpenX is strong in Europe. It's the most efficient SSP in the European market with 28% total efficiency. In the US OpenX takes only the 12th position in the Total Efficiency Rating. OpenX wins 67% of all header auctions it participates in. This SSP would be a great addition to publishers with a predominantly European audience.
AppNexus is the most stable SSP on the market. Its Efficiency in Europe and North America is almost identical - 22.7% and 23% respectively. AppNexus takes the third position in Total Efficiency Rating on both markets.
FAN is less competitive and efficient in Europe. Despite the higher Desktop Bid Rate, 45% in the EU vs 20% in the US, FAN wins only half of the auctions it participates in. In the US it wins more than 80% of auctions. As a result, FAN's total efficiency dropped from 41% in the US to 26.4% in Europe.
Rubicon is only the 7th SSP in Europe in terms of total efficiency which is 10.5%. Rubicon wins more auctions in Europe, 49% vs 38% in the US for desktop and 63% vs 30% in the US for mobile. However, Rubicon bids only for 21% of all European
ad requests. The low bidding rate greatly affects total efficiency of this SSP on the EU market.
Only 2 SSPs bid more than to 50% of all ad requests. If you have 5 bidders and each bidder responds to 50% of ad requests, the probability that all of your SSPs compete in the header simultaneously is 3%. The problem of low competition in the header is discussed in our recent article on adexchanger.com.
Header bidding wins only 30% of auctions in the ad server which might be a result of low competition in the header. The low competition affects the performance of other elements of your ad stack such as Google AdExchange. When bidders rarely bid simultaneously for the same impression, low bids are often sent to your ad server.
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