(TL/DR? Skip to results.)
Yesterday I wrote that even though social networks currently combine targeted advertising and private user data collection, doing them both is not a requirement for running a profitable social network. The networks can just focus on the former, that is focus on the harvesting and selling of user data, and dispose of the advertising part altogether.
Having the social network and the ad network on the same domain (for example facebook.com) does make things slightly easier for the social network operator, because users may have switched off so-called third party cookies which are stored and read from a different domain (for example doubleclick.com).
The reason why the average user would block third-party cookies is because these cookies are almost exclusively abused for tracking users behind their backs.
How much of a problem is it to advertisers that users block third-party cookies? Not much. Users are typically reluctant to tinker with browser settings, therefore it depends on the web browser makers and the sensible defaults they choose whether an aspiring social network can plant cookies that another domain may read.
I decided to look into the defaults of modern web browsers, but could not find much information.
Here are some data points:
That leaves some browsers unexplored. Since checking the browsers on my computer was probably going to be easier than Googling anyway, I decided to take that route.
Table: default cookie settings for some web browsers in 2014.
|Browser + version
||Default cookie setting
|Google Chrome 37
||Allow (all?) cookies
|Microsoft Internet Explorer 11
||Allow some third-party cookies
|Mozilla Firefox 32
||Allow third-party cookies
||Apple iOS 7
||Allow local cookies?
||Google Android 4.0
||Allow (all?) cookies?
As you can see the answers are ambiguous at times and don’t square with the results I linked to, but it would appear that currently most web browser will let sites track you across domains using third-party cookies.
A note about methodology. This was a quick study to find out what the default cookie settings are. For that, I needed to restore browser defaults and that was not always possible. The mobile devices (iOS and Android) had no way to restore settings to a default so I had to assume that these were the default settings.
I do tinker with my desktop browsers but I rarely do so with my mobile devices, so it’s a reasonable guess that the aforementioned settings are the default ones, I just cannot be absolutely sure.
Another problem was that browser manufacturers use different settings, different terminology and sometimes translations which can make it hard to find out which is which.
Most browsers speak of ‘allowing’ cookies, iOS Safari speaks of blocking them.
The reason I report Chrome’s default as “allow (all?) cookies” rather than “allow all cookies” is because I don’t know if “indirecte cookies” is their Dutch translation of “third-party cookies”. If it is, you can remove the question mark and conclude that Chrome allows all cookies by default.
Internet Explorer has a return-to-default button just for privacy settings, which is much appreciated, and a number of sensible settings collections. Unfortunately the explanation of what these settings mean is rather opaque. For instance I don’t know what are “cookies that can be used to contact you”.
Firefox’ default is also a ‘sensible’ setting which tells you only in the most general terms what it does, namely that the browser “will remember your browsing, download, form and search history, and keep cookies from websites you visit”.
You can choose to use custom settings and if the defaults for these settings can be assumed to be the same as the ‘sensible’ settings, then their third-party policy is clear if perhaps not sensible: “Accept third-party cookies? Always.”
Safari lets you choose to block cookies: “Always”, “From third parties and advertisers” and “Never”. I assume “and advertisers” is not a separate category from “third parties” and was just inserted to make it clear that these are tracking cookies, but again, that’s just an assumption.
The Android Browser’s setting is the least complicated of all, you can choose Cookies or No cookies, and if you choose the latter I assume most of the useful services on the web become off limits to you. But are there really people who bank online using their smart phone and an operating system made by Google?