Podtrac Measurement, Verified by IAB Tech Lab

IAB Podcast Measurement Technical Guidelines Version 2.0 Details

 Podtrac announced today that its measurement system has been given an official “seal of approval” by the IAB Tech Lab as compliant with the IAB Podcast Measurement Technical Guidelines Version 2.0.  Podcast audience counts for any publisher or podcast provided by Podtrac’s redirect measurement system, including those listed in its dashboard and its monthly Podcast Industry Rankings, are verified compliant through the IAB Tech Lab program.The IAB Public Disclosure for Podtrac is available here.


Since 2005, Podtrac has provided independent podcast measurement for any podcast, publisher or network, regardless of where they choose to host their podcast episode files, to thousands of podcasts including the majority of top podcast publishers.  In 2016, the IAB Podcast Working Group, comprised of more than 40 member companies, including podcast publishers and hosting companies, developed the IAB Podcast Measurement Technical Guidelines Version 1.0 published in 2016 and the Version 2,0 guidelines published in 2017. The IAB Tech Lab Podcast Measurement Compliance Program process is an opt-in initiative, and includes a rigorous audit of systems and technologies used to produce counts consistent with the guidelines.  

 Certification Details

Per the IAB Tech Lab Podcast Measurement Compliance Program, Podtrac is the first company to be verified by the Tech Lab for:

  1. Counting podcast audiences through a measurement redirect. Verified audience counts for any podcast measured by Podtrac are available from Podtrac regardless of where the podcast files are hosted.

  2. Identifying multiple podcast audience members behind shared IP addresses.  A significant percent of podcast audiences access podcasts in shared IP environments, such as mobile network NATs and corporate firewalls. Podtrac’s advanced systems and analysis count unique individuals in these scenarios.  

For those interested in more details, below is more information about each of these topics.

1- Counting podcast audiences through a measurement redirect 

Podtrac’s redirect measurement system is certified as following the guidelines’ goals of excluding download counts having less than a minute of downloaded content.

The Challenge

Before Podtrac, the IAB Tech Lab had not given a compliance seal to any company for counts and analysis gathered through a measurement redirect.  That’s because a key challenge is removing counts for podcast downloads that don’t achieve the Version 2.0 guideline’s minimum 1-minute file threshold level as described in server log files, and standard redirect measurement systems don’t have access to this data.  Podtrac’s previous system accounted for partial downloads, but the guidelines provide an option which encourages innovation to employ “a more sophisticated mechanism.”  

The Solution

Podtrac developed a new proprietary system released as part of our algorithm updates on June 1, 2019 that provides an accurate measure of partially downloaded podcast files. Per the Version 2.0 guidelines, Podtrac uses more advanced algorithms that factor in a correction for partially downloaded content than the example process listed. Podtrac uses advanced algorithms to identify and remove partial downloads in real time using data captured through its redirect.  Podtrac disclosed the complete details of its process and analytics to the IAB Tech Lab and an independent technical auditor, and after a rigorous review, they agreed that this produces counts for partial downloads consistent with the guidelines.

 What this means to publishers and advertisers

Podtrac solved the critical task of accurately removing partially downloaded podcast files that don’t achieve the minimums specified in the Version 2.0 guidelines using a redirect measurement system, by developing a new method that achieved certification.  

Now, with Podtrac:

  • Any publisher can access verified audience counts for their podcast today regardless of where they host their episode files by using the Podtrac redirect.

  • The industry has a podcast industry ranking with audience counts officially deemed compliant with the IAB Podcast Measurement Technical Guidelines Version 2.0.

 As of today, Podtrac is the only podcast company using a measurement redirect to have addressed the partial download requirement to the satisfaction of an independent auditor and the IAB Tech Lab, which means that when it comes to redirect podcast measurement systems, only counts from Podtrac are verified as compliant with the Version 2.0 guidelines.

 2 - Identifying multiple podcast audience members behind shared IP addresses. 

Podtrac’s algorithms for counting downloads from multiple users with the same device types and client software behind shared IPs are certified as consistent with the guidelines.

The Challenge

Podcast publishers and advertisers have asked if we can identify multiple users behind shared IP addresses such as corporate firewalls and mobile networks.  Increasingly, internet traffic generally, including podcast traffic, is conducted through IP addresses shared or recycled among multiple users, such as mobile network NATs (Network Address Translation) and corporate firewalls.  If two or 2,000 individuals per day download a podcast episode using the same device types and client software behind the same IP address, then the sample algorithm listed in the Version 2.0 guidelines count them all as a single listener.  This undercounts that podcast’s audience.  It’s why publishers have asked us to solve for accurately counting the number of users who download their podcasts in both single and shared IP environments. 

An important aspect of the Version 2.0 guidelines is providing a sample method for podcast analysis, while also encouraging and supporting discovery and innovation.  The Version 2.0 guidelines state generally that “companies are allowed to use more sophisticated mechanisms” than the specific methods listed in the guidelines. 

 The Solution

GIven the breadth of Podtrac’s measurement reach, Podtrac is uniquely positioned to:

  • Size the instance of multiple users downloading the same episode files in the same day using the same IP address

  • Develop and apply a more sophisticated method of analysis to our measurement system to avoid undercounting delivery.

Podtrac has developed proprietary algorithms to properly count listeners behind shared IP addresses. Podtrac uses a variable measurement window, including a 24-hour window and windows shorter than 24 hours.  The variable window was released as part of our algorithm updates on June 1, 2019.

The system is consistent with the Version 2.0 guidelines, which state: “No window is perfect, but shorter windows open up a risk of double counting requests and so should be done with care. Conversely, longer windows risk undercounting delivery via recycled mobile IPs and true multiple listens. Companies are allowed to use more sophisticated mechanisms…”

 Podtrac’s variable window is the best solution, yielding more accurate results. On average, the difference between a 24-hour window and Podtrac’s variable window is 6.5% across all shows.  After a rigorous review, the IAB Tech Lab and an independent auditor reviewed and accepted Podtrac’s variable analysis window as consistent with the V2 Guidelines.

 What this means to publishers and advertisers

Podtrac solves for the age-old question of identifying and separating downloads from the same individual and unique individuals behind shared IP addresses. This approach is consistent with the IAB Podcast Measurement Technical Guidelines Version 2.0, which encourage innovation with a provision for “more sophisticated mechanisms” which are increasingly important in a mobile world.  

Although a 24-hour window in the sample algorithm provided for in the Version 2.0 guidelines produces reasonable results and is useful to companies that aren’t in a position to develop more sophisticated systems, Podtrac’s variable window and analysis identifies audience members previously hidden behind shared IPs.    

Publishers and advertisers can be confident in the counts Podtrac provides.  The longest-running podcast measurement system -- currently measuring more than a billion downloads a month across tens of thousands of podcasts -- is now verified as compliant by the IAB Tech Lab.