Day: 15 June 2025

For anybody who works with web-based content, the “impression” is a very important metric. It used to be that the world talked about “hits”, but I think we’ve moved on from that: it’s the least descriptive and most open-to-abuse metric by which we measure successful web content.

So if you are a web content publisher, impressions are important. Essentially, every page somebody views (and it really should be a somebody and not a web crawler, spider or robot) is counted. The total number of page impressions is one measure of your website’s popularity. Lovely. Such counts help websites understand what’s popular and what’s not and help them refine what they do.

As the boffins who looked at all this data got smarter and web analytics became big business, people acknowledged there were other metrics. The number of pages read is not always a good indicator of success. Is it a million pages read by one person or by a million people, only reading a single page? Analytics progressed to give us visits and sessions. These “smarter” metrics accounted for whether individual browsers looked at more than one page and over what period of time. If I read 5 pages in the morning, that was 5 impressions and 1 visit. 10 more pages on your site in the evening was another visit and another 10 impressions, but crucially, I was one unique user.

Ooops, I just threw in another metric. Sites needed to get better at understanding all these impressions and visits because, while nice, numbers didn’t tell them much about their audience. So, unique users became important because they told sites how many people came to their site. From that, sites can understand how many visits users make and how those visits translate into all those lovely page impressions. It’s like a TV company telling us how many people watched Friends last night. It’s nice to know.

But, generally, websites don’t know who you are (unless they are one of those that let you create a user name and log in). So they started to use cookies to identify your browser. That statement is actually quite important. Sites don’t know who you are; they just assign a unique number to your browser to help them better understand all these unique users. Importantly, if you delete your cookies – or sometimes use another web browser – then they don’t know that you’ve done that, and those actions can inflate the numbers for the site. Still, TV and radio are measured by small samples of people filling in diaries, so all systems have some margin of error and cookie deletion is generally understood, accounted for and accepted.

So, why am I talking about all these web analytics terms? Well, that’s for two reasons.

Firstly, any website that sells advertising needs to tell advertisers approximately how many people will see the advertisement. They do not want a scenario in which one person has seen all one million of their advertisements. With apologies to my friends in advertising agencies, let’s say that Advertisers tend to prefer that a range of people see their messages. These measurements are great for helping sites understand audiences.

As a side note, sites generally like these numbers to be as big as possible because it makes them look good. They have a range of tactics to make the number look as large as possible (such as automatically refreshing the page or a part of the page to make it appear as if there were another impression). Properly managed websites that sell to big advertisers tend to have their numbers audited by companies like ABCE. ABCE, if you like, helps advertising agencies know that the sites aren’t lying about these impressions, visits and unique users.

Secondly, I am trying to place these terms in context ahead of the next piece I am writing about another important metric to those websites: the ad impression. But that’s for another day.

Whenever you’re working with a site that starts quoting impressions, visits and unique users, it’s worth asking how they were collated and whether they are audited. Are the numbers for the specific site in question or for a “network” or collection of sites owned by the same publisher? Is the publisher using auto-refresh to inflate the numbers, and are those numbers both collected and audited by reputable experts in this field? (It is worth noting that auditing can be expensive for small sites, but you do need to understand how they have come up with the numbers, and you should try to get an understanding of both the number of pages viewed and the number of users that make up those views.

I must caveat this by noting that I am not a web analytics expert. Such folks will be able to explain the nuances of these measurements in more detail but, think of this as a handy cheat sheet so that you’re not impressed by somebody who talks about their large number of page impressions and then doesn’t put them into context for you.

If you like, I’m performing a public service.

Update: The second part of this mini-series about ad-impressions is now on the site.