Mobile Web - Header Bidding Concepts and Practices

Thank you for choosing Facebook Audience Network as your Header Bidding monetization partner on mobile web. This document will walk you through some best practices that have resulted in positive results for Audience Network publishers. As you begin implementing Header Bidding, please be sure to reference these practices.


Header Bidding is a way for publishers to establish an impartial and open auction over their ad inventory, by offering every ad opportunity to multiple demand sources at the same time, significantly increasing competition and monetization.

Key Concepts and Practices

Match Rate

Audience Network serves ads only to Facebook matched users. If there is no match, no ad is served resulting in no fill.


On Audience Network, viewability of a mobile display ad is defined as 100% width and 1px height. Viewability is a critical factor in the calculation of the final bid price. Every bid on Audience Network is adjusted by the predicted probability of the ad being viewable. Therefore, for low viewability ad units (<65%), the bid price is on the lower end whereas high viewability ad units (>65%) have a larger probability of receiving higher bid prices.

Focus on Advertiser Value

At Facebook, our focus is on creating real outcomes for advertisers, such as end-user engagement and conversions, and rewarding quality publishers based on the value they generate for advertisers. This translates into a focus on metrics like CTR and CVR. Publishers that create ad experiences that drive engagement generally result in competitive CPMs.

Model Calibration

Facebook uses machine learning models to run an auction optimized for advertiser objectives. When Audience Network is first plugged into a publisher's inventory via Header Bidding, these models take approximately 7-10 days to learn about the publisher's audience and supply and calibrate accordingly. Calibration can be expedited if the volume of requests and impressions is >500K per day per placement.

Placement Position

Performance is calibrated on the placement level, so publishers should create a separate placement for each ad location on their mobile website. For example, a publisher should create a placement for all 'in-article above-the-fold ad units' on the site. Another placement should be created for the 'bottom of the article page ad unit'. Similarly, a publisher should also consider the page type when creating placements. For example, home pages and section pages may have separate placements to article / content pages. This could vary from publisher to publisher based on their setup and traffic volume.

Lazy Loading

Lazy loading is a concept where the loading of page content is delayed until the point where its requested by the user. In other words, on demand content loading rather than loading content unnecessarily. The same concept can be applied to how ads appear on a mobile website which can help improve an ad unit's viewability, bidder win rates and bring efficiency and reduce wasted bandwidth on a mobile webpage. A few options to utilize this technique are: 1) Lazy load the header bidding auction and the call to ad server or 2) Conduct the auction in the header and lazy load the call to ad server.


Audience Network supports 300x250, Full Width and Native ad formats. As a standard, all publishers should start with a 300x250 ad unit. Once the Header Bidding integration is up and running, it is advised to test and switch to the Full Width format. If a publisher has in-house design resources, Audience Network provides a spectrum of tools to build and customize native ads.


For all the pros of Header Bidding, latency is definitely a con that is well known. Publishers, Wrappers and Bidders alike are looking for ways around this problem. Most publishers set a timeout of 500ms on the low end and 1500ms on the high end in the wrapper based on overall site load times and performance. Also, moving header bidding to server-side is supposed to resolve issues related to latency. Testing of this methodology is in the works.

Refresh Rate

The refresh rate determines how often a new ad impression is requested on a mobile website. A publisher can choose not to refresh ads or to refresh every 30 to 120 seconds. It is advised that ads persist for 60 seconds or longer, depending on the functionality of the website. This ensures users have enough time to engage with ads, providing the best performance for both advertisers and publishers.

Bid Lifespan

Each web bid is valid for 10 minutes, or 60 minutes for instream video bids - any impressions served on bids older than 10 minutes (60 minutes for instream) will not be paid.