How accurate is ComScore

Comscore: what they do and how their rankings (actually) work

What does Comscore do?

Comscore is a global media measurement and analytics company. The company offers third party measurements of audience demographics and media performance across multiple media. By their own definition;

Comscore is a trustworthy partner for the cross-platform planning, processing and evaluation of media. With the science of transforming data and broad viewership insights for digital, linear television, over-the-top (OTT) and moviegoers, we are a powerful third-party source for reliably measuring cross-platform audience numbers.

The idea behind third-party audience tracking is to bring transparency to the media and marketing so that companies can use data to drive growth.

What are comscore rankings and how do they work?

Comscore's rankings are based on the audience measurement services they sell / offer to publishers. The Comscore media matrix, which was accredited by the Media Rating Council (MRC) in 2016, uses a series of “panels” to measure the audience. These audience registration services are often observed by advertisers and agencies. The main differentiator between Comscore and other web analytics solutions (like Google Analytics) is that their primary goal is to measure exactly who an audience is and what their consumption behavior is like. It takes a more traditional way of looking at human visitors as many of the audience tracking mechanisms through television and other ancient media are less objective than digital. In addition, their panel method defines page views across all pages. However, the panels and measurement techniques used by ComScore and competitor Neilson both rely heavily on the voluntary participation of all parties in the network to obtain their composite rating. This means that audiences, publishers and agencies / advertisers all have to bow to the will of these third parties if they want to participate in these systems.Traditionally, the persecution of the public has been fraught with criticism. But recent acquisitions by big tech companies like Moat have shown the value of tracking across the network. Because both publishers and advertisers have long relied on a decision maker to carry out campaigns.

Are Comscore Rankings something advertisers and publishers are interested in?

Advertisers and publishers often care about comscore rankings, but not in the way many might assume. The vast majority of advertisers likely have no idea what they are and pay little attention to these services. Agencies and top 50 branded publishers often pay much more attention to these metrics as they are typically a point of contention when negotiating advertising contracts. Comscore and its competitors act as intermediaries. If a publisher doesn't include comscore pixels in their pages (often because they slow down web pages and can cause errors), they won't count in comscore rankings. But that does not mean that an advertiser will not address a target group on his side ... ... Advertisers who use Comscore when buying through an agency will therefore still address target groups on publisher pages who neither use Comscore nor their competitors.So what's the point when you're a digital publisher? It depends on a publisher's goals. There is little monetary incentive or benefit to any digital publisher depending on what industry expert you ask. However, it is a moot point in the competition between some of the long-lived media brands that previously relied on these scores or rankings for TV campaigns.

What does the comscore panel measure?

Measurements from the panel include Comscore's rankings - a monthly list of the top 50 digital websites on the Internet, ranked from highest to lowest based on the number of unique visitors.

Who or what are the comscore panels?

The “panel participants” are identified by Comscore as either private or work-based machines. These must be personally owned by the panelist (or household) to qualify as a home panelist. Computers owned by an employer are considered work computers. Some of the things that the panel methodology can register are unique visits.

  • Internet activity from all web entities regardless of browser type
  • Private Browsing Sessions / Secure Sessions
  • Content elements / streaming / instant messaging
  • Web-based technologies and protocols

The panel is then weighted and projected onto the Internet worlds at home and at work in the United States, which allows the behavior of panelists to be projected onto the entirety of Internet users at home and at work in the United States.

How effective is the Comscore panel measurement system?

Comscore's panel measurement system appears to be accurate and effective. Out of curiosity, I tested Comscore's numbers for a digital domain in the Comscore Top 50 ( to see if the number of unique monthly visitors recorded was comparable. To do this, I went to a competitor of Comscore, Similarweb. Comscore’s count for’s June 2020 unique monthly US desktop visitors was 90.42 million. After evaluating the numbers, Similarweb’s was 90.64 million. They were both almost the same height. The fact that Similarweb's mapping was slightly higher is most likely due to the fact that the numbers I used to calculate were rounded up to the hundredth decimal and not exact.

Why are the comscore traffic numbers lower than those in Google Analytics?

The comscore traffic numbers are lower than those in Google Analytics, mainly due to differences in tracking methods. Here are some of the reasons why: Attribution: Google Analytics defines a session timeout as 30 minutes of inactivity. They also have additive rules for attribution. This means that 30 minutes of inactivity add up to a new session. Comscore, on the other hand, has a 3-second window to count as a visit. Anything less than 3 seconds leads to exclusion. Multiple browsers: Comscore eliminates visits from multiple browsers and multiple screens (cell phone, desktop, etc.) Non-human traffic: Comscore ignores (or eliminates) bot traffic, and Google Analytics counts all visits, regardless of whether it is a bot or a real user. This difference is the main factor behind Comscore's lower traffic figures. Note: Google now offers a bot filtering setting to eliminate invalid traffic. Data projection: For Analytics, Google uses the "real-time" data and then records and stores the anonymous data. Comscore makes estimates based on the pool of panelists tracked via plugins or cookies.

A Comscore whitepaper revealed that clearing cookies could lead to overestimates in how the servers measure the size of the online audience. Without adjustments, the reports on the audience on the server's sides can grow up to 2.5 times the actual number of unique visitors.

Why do ad networks work with Comscore?

Most ad networks in the Comscore top 50 require publishers to assign their traffic through a traffic assignment letter. This adds your traffic to your “Total Unique Visits” count and ultimately increases the total number of your Comscore visits.

Put simply, ad networks and ad management platforms work with Comscore because they can use your traffic to look “bigger”. Let's break that down a bit.

That way, when they're trying to attract agencies, direct advertisers, etc., the audience is big. This will benefit you as an affiliate, provided you are able to deliver on their promise to attract these kind of big advertisers.

From an ad network perspective, you will likely never be able to negotiate the same way a network would be for you. Most networks are dealing with the billions of ad impressions per month, and that is what advertisers "look for" when trying to bargain.

For those who are more skeptical, some have speculated that the ad networks that pay the high annual price that Comscore measures your audience, just want to look as big as possible to attract the next publisher in their business pipeline.

What is a traffic assignment letter and why are some ad networks asking you to sign one?

A Traffic Assignment Letter (TAL) is used to assign a publisher's traffic to the network they are working on. Once this traffic is assigned, the ad network can negotiate advertiser deals for the network as a whole and for your individual website. The bigger the network gets (in the eyes of Comscore / Quantcast / etc) the better the deals they can negotiate. At least that's what is intended.

Publishers sometimes forget that they can only map traffic to one place. Most ad networks usually have you sign a contract to confirm that you've formally signed your traffic to live under their network's umbrella. In addition, you cannot sign any other deals in which you transfer your traffic to a ComScore etc. to other third parties.

Below is an example of a Nielsen Traffic Assignment Letter.

Are there any disadvantages in overwriting your traffic to a comscore unit?

At least not on the surface. And the ad networks, which are allowed to include your monthly traffic numbers in their total comscore number of unique visitors, don't want you to think that way. The whole purpose of this is to make yourself look bigger, in order to bigger Attract advertisers. But because it seems so simple and innocent, they fail to mention the possible downsides. The downside is that You turn off your ability to diversify certain sources of income. You are (most likely) giving a larger part of your earnings to the partner. And the fact that you've signed an exclusivity agreement? This prevents you from making other network deals. This is one of the reasons Ezoic’s Ad Tester and our entire ad testing platform were built on the pillars of transparency, the value of split testing, and no contract. So what exactly do I mean by all of this?

Remember: Most ULL contracts state that the new digital asset (or ad network) is now the your only representative is and which providers they use to replenish all other inventories (outside of direct sales), that you cannot useIf the ad network is well versed in the industry it is most likely using premium providers and does not allow you to drive traffic yourself. Instead, this inventory will run through your page at a certain percentage of the revenue.

Note: This may not apply to all ad networks as every deal is different. But in general these aspects of Traffic Assignment Letters apply.

What can publishers do to protect the value of their audience?

The best that publishers can do to protect the value of their audience is always remain skeptical. Read the fine print. Don't sign contracts if you can avoid them. Check with your ad network to see if you can weigh ad management against someone else. Because in reality, a head-to-head comparison is the only way you'll ever know who is making you more income. Due to the seasonality of ad prices, fluctuations in ad demand, and frequent Google Core updates, testing one ad network one month and another the next is not a fair comparison. Therefore, you will not know for sure who was better. In reality, there are a ton of fraudulent players in the advertising industry who are pulling money out of the pot. But the same players do not bring back any added value. A quick look at the Lumascape display shows you how overwhelmingly bloated the advertising technology is. According to research by Technology Business Research, only achieve out of every dollar spent on program advertising 40 cents the actual consumer. As incredible as this may seem, a whopping 60 cents (or more) of every dollar is swallowed up by one of the hundreds of units shown in the graphic below.So it goes without saying to be careful. Realize the value you have as a publisher and protect your audience by questioning things and staying skeptical.

Will comscore be just as important to advertisers in the future?

A lot of people don't believe that. Over the years Comscore has received mixed (praise and negative) sentiments in online publications and also in forums like Reddit and Quora. The loudest complaint? Is that Comscore's entire business model is only beneficial for the digital objects in the Comscore Top 50. Certain incidents in Comscore's history give weight to these negative feelings. In 2010, after years of complaints against Comscore, the undercount of their audience came to a head (due to the use of a purely panel-based measurement without the use of tracking pixels). Quantcast and Google pressured them for it free Offer tracking pixels that pages could use to count their traffic. Comscore then developed a "hybrid" model that uses both panels and tracking pixels on the page. Comscore then passed the tracking pixel on to paying customers free of charge. Everyone else was upset because they had to pay Comscore $ 10,000 or keep their traffic counted as before. In 2020, the minimum payment for using Comscore's services is $ 9,600 per year. Since then, their numbers have been close to historic lows. One of the reasons for the decline can be traced back to the third quarter of 2019 when the Securities and Exchange Commission accused the former Comscore CEO of being involved in a involved in a fraudulent plan to overestimate revenue by approximately $ 50 million and make false and misleading statements about key performance metrics.Objectively speaking, Comscore's track record doesn't exactly help the cause. That's not to say that Comscore's measurement tools aren't valuable, but one wonders if the advertising networks in the Comscore top 50 are just "bigger is better" to attract the biggest advertisers. Or is it more of a selling point for potential publishers to join your network? It could be a mix of both, maybe.


Ten years ago, Comscore was a sign of certainty that many publishers and advertisers were keen to get behind us. However, some argue that advertisers have always known that comscore rankings and campaign effectiveness are not that closely related. In today's world, digital publishing and the advertising industry as a whole are more performance-oriented. These leaderboards are just not as important as they used to be. More important today is the audience itself and how valuable it is (directly) for advertisers. There are very few scenarios where you have a large ad network needto act as an intermediary. Especiallywhen that ad network forces you to sign a contract. So you see how the pieces of the puzzle come together here. While the largest publishers may find their audience measurement services valuable (even at their expensive price), the comscore rankings themselves are objectively no longer as important as they were ten years ago. That said, Comscore is still a big name and is respected by many in the advertising industry. So if you are a successful publisher with a large audience, judge for yourself. Ultimately, it is your audience, and don't let anyone (person or ad network) try for a moment to convince you that you need them to be successful. Because that's so far from the truth. You need you. Because without you, they can't keep getting bigger and bigger ...

Allen is a published author and accomplished digital marketer.The author of two separate novels, Allen is a developing marketer with a deep understanding of the online publishing landscape. Allen currently serves as Ezoic’s head of content and works directly with publishers and industry partners to bring emerging news and stories to Ezoic publishers.