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How LEAN Can You Get? A Scale and a Score Will Tell You

By Brendan Riordan-Butterworth


Six months ago, the IAB Tech Lab released the LEAN Principles.  These were a product of research and discussion with thought leaders who championed a clear path to better user experience in advertising-supported digital media – a must in a world where too many consumers were rejecting kludgy, gummy, slow ads and sites by installing ad blockers. Since their publication, the digital media world has embraced LEAN – which stands for advertising that is Light, Encrypted, AdChoices-supporting, and Non-invasive – and a growing number of companies have been developing their own take on what it means to be LEAN.  This enthusiasm is wonderful, and has spurred further action in the Tech Lab.  After all, without coordination, we’ll end up with publisher-specific LEAN criteria that are costly and complicated to meet industry-wide.

After a great deal of research and reflection, we believe the best and fastest path to encourage universal adoption of the LEAN Principles is to introduce a public LEAN-scoring system that will publicly rank publishers, advertisers, and by extension agencies on their adherence to the principles. By embodying the concept of speedy, safe, and agreeable advertising in an objective score, the industry will have a market mechanism that will drive continuous improvements in user experience, just as nutritional labeling has driven consumer demand for and manufacturers’ marketing of more healthful foods.

Think of a LEAN score as your Fitbit for healthier advertising. Here’s our plan for convening the entire industry to get us LEANer.

Getting to Guidance

Tech Lab’s mission is to discover efficiencies and reduce friction in the digital advertising marketplace.  In the context of LEAN, we’re building consensus as to what constitutes LEAN by soliciting data, research, and input from subject matter experts – and making use of these insights to develop clear, market-wide guidance.

It’s important to remember that guidance issued by IAB historically has been based primarily on the consensus of subject matter experts, brought together in our working groups.  With LEAN, we’re emphasizing research and data as inputs into the development process:

  • First, by gathering data and engaging in primary research, we provide those experts with information necessary to develop data-supported guidance.
  • Second, by establishing a clear process for verifying and onboarding data- and research-supported criteria developed by our members, we have a path to consensus that leverages early mover efforts.

In order for the LEAN guidance to be effective, it must be well thought out and well supported by research and data.

Working Group Roadmap

Through 2016, our goal is to build industry-wide consensus around criteria for the individual components of LEAN. When is a page too heavy? When is an ad too heavy? What makes an ad too fat? Are all encrypted pages alike? Must all ad tags be encrypted? Is auto-play audio always disruptive, in all contexts, or are there some environments where consumers find it acceptable? Towards the end of the calendar year, we will evaluate this roster of established criteria with an eye to understanding the impact of each individual criterion relative to all others in order to establish a scoring system.  This will provide a structure for decisions about what advertising experiences meet the goals across consumer, publisher, and advertiser requirements.

This quarter, we’re formalizing the process of onboarding data and criteria, starting the public discussion about initial guidance, completing some initial user experience testing, and educating the market on our vision for LEAN.

Over the summer, we expect to be onboarding data and criteria from partners and iteratively publishing LEAN criteria.

During the final quarter of the year, we’ll be moving to understand the relationships among the published criteria in order to establish a simple to understand, context-appropriate scoring algorithm.

Initial Guidance

File Size

IAB has long issued file size guidance. As such, we recommend that, in order to be compliant with the LEAN Principles, creative must be less than or equal to the maximum file sizes established in current IAB guidance, updated by the IAB Tech Lab team to reference HTML5 ad requirements.

We expect this guidance to continue to iterate through the years, in order to account for new platforms, technologies, and user tolerances. Tools like our HTML5 Ad Validator are available to help evaluate ads against current guidelines.

Ad Load Time

The range of factors that might affect user experience make measuring user experience difficult, even in a purely technical sense. Each user will have different considerations for available bandwidth, CPU, and RAM, as well as geographic proximity to the server, screen and window size, and more. We’ve not yet been able to establish the technical attributes of a “normal” user, and expect that this will vary along demographic lines.

Therefore, we recommend that, in order to be compliant with the LEAN Principles, the load time that a user experiences when visiting the content or service must be regularly evaluated and kept to industry guidance on rendering time per research results on user tolerance and negative user experience.

At the same time, it seems clear from all available research that there is a threshold for page load-times that should not be crossed, without risking consumer disaffection. It is equally clear that some factors – such as excessive and redundant data calls from an ad unit – contribute inordinately to these barrier-busting load times. Our goal is to identify the right thresholds and their contributing factors, and incorporate them into our LEAN scoring mechanism.


A year ago, I joined the chorus calling for broad adoption of HTTPS. With projects like Let’s Encrypt making certificates readily available to all comers, the need for the entire supply chain to support HTTPS requests has never been stronger.

As such, in order to be compliant with the LEAN Principles, all resources delivered to an HTTPS parent frame must be similarly delivered over HTTPS.

The days of simple errors for mixed content are ending – Firefox, Chrome, and IE all block active mixed content by default. Ensure end-to-end consumer privacy and protection, avoid discrepancies and unnecessary user-facing errors with full support for HTTPS.


The Digital Advertising Alliance’s AdChoices initiative is one of the most successful self-regulatory programs in the history of advertising. Every month, trillions of ad impressions are delivered with the now-ubiquitous AdChoices Icon, which signals to consumers that, with a click, they can go to a page and learn who is using their data and how – and opt out, or opt in, to each individual user of their data.

AdChoices is an amazing opportunity for a consumer to interact with an ad in a way that doesn’t signal specific interest in the ad itself. In addition to the required opt-out, some implementers are using the icon to solicit additional feedback about the ad experience directly.

Providing mechanisms for feedback and choice is an important part of having a conversation with consumers. This is a starting point into the conversation about the importance of additional choice mechanisms, like choice about the cadence of ads across a visitor session, and the options presented in the Publisher Ad Blocking Primer.

Overall, we recommend that, in order to be compliant with the LEAN Principles, all ads that are selected for delivery through the use of an online behavioral advertising (OBA) or Interest-Based Advertising system must bear the AdChoices Icon – which means that all advertisers and all publishers must be members of the Digital Advertising Alliance.


Preliminary research implies strong consumer demand for skip – the research from IAB UK indicates that unskippable video ads are a primary driver for installing ad blockers, and that having an option to skip would cause some ad blocking users to reconsider.

Issuing guidance on skippable ads also aligns with existing IAB guidance on the availability of close buttons – we recommend these for any ad that overlays content.   Therefore, in order to be compliant with the LEAN Principles, pre-roll video ads must include the opportunity to skip after no more than 15 seconds.

Non-Blocking Scripts

Some ad units intentionally delay the delivery of content – like pre-rolls or interstitials. Others aren’t meant to, but do. When ad units aren’t intended to block delivery, they should use techniques to minimize the risk of interrupting content loading.

Therefore, we recommend that, in order to be compliant with the LEAN Principles, all ads delivered concurrently with content or services be requested in a non-blocking manner – i.e. they must use technology conventions that will allow the content or service to be delivered to the visitor without delays introduced by the delivery of the advertisement.

While this is being examined, also evaluate page jitter during ad loading – when content and scroll position shift due to supplementary ad loading.

Next Steps

The Tech Lab’s Ad Blocking Working Group is now meeting to build and prioritize our backlog of criteria, with emphasis on understanding criteria specific to scenarios outside of the desktop web.  We’re also building the process for consistently onboarding 3rd party research.

While the path to LEAN scoring will have some rocks in it, we believe there will be more pebbles than boulders. The digital advertising and media industries are ready for an easy to understand mechanism by which they can judge whether their ads and sites are contributing to positive user experiences. Perhaps more importantly, a LEAN score will encourage all participants in our ecosystem to raise their game, and make user experience an essential currency for marketers, agencies, and publishers alike.


Brendan Riordan-Butterworth

Director, Technical Standards