The Public Suffix List Drama From IOS Updates
The Public Suffix List Drama From IOS Updates

By: Mike Hudgins

To say that discussion around the IOS 14 update has been prevalent in the marketing world would be an understatement. It's actually insane how much is changing so fast. I have written about this a lot in the past few months, but this time I just want to focus in on what is happening between Facebook and the Public Suffix List. 

What is the Public Suffix List?

Taken directly from the wiki: The Public Suffix List (PSL) is a catalog of certain Internet domain names. The term is also known by the form effective top-level domain (eTLD). The Mozilla Foundation maintains suffix list for the security and privacy policies of its Firefox web browser, though it is available for other uses under the Mozilla Public License (MPL). For those interested, here is a link to the actual list

Functionally, domains on the Public Suffix List do not share cookies with their subdomains. This means that if our site was on the PSL, would be treated as a a completely separate domain name to (and we would lose cookies on the domain you are reading now). Think of this like Each website has its own unique myshopify domain name, and each of them is completely separate from one another.

What are the Limitations of being on the Public Suffix List?

The top level domain name can no longer use cookies. Say I own, and I charge businesses for a platform they can use to sell tickets. If I use to recruit other businesses to sign up for my platform, I will no longer be allowed to advertise or track users on that page at all. There are tons of functionality limitations that comes with not being able to use cookies. Businesses should really think about whether or not they belong on the list. 

What's the Problem? 

Facebook created a help article about the IOS Updates where they essentially cited the PSL as a method of circumvention of the subdomain restrictions. I read a ton of comments on the GitHub, and Facebook is actually updating their own help articles based on the suggested wording of dnsguru, one of the PSL's most active volunteers. 

The PSL volunteers responded by updating the PSL instructions to include circumvention of IOS tracking for the purpose of Facebook Marketing Campaigns as an automatic wontfix. This means that anyone who submits a request to be added to the PSL based on Facebook Marketing will be automatically declined, even if they fit the criteria in every other regard. I sympathize with the PSL volunteers that they do not want to become unpaid volunteers for Facebook; but I am not sure I agree with the automatic rejection. I found an excellent example that I will outline below:

There was a GitHub pull request from that outlined their reasoning for wanting to get on the PSL. They use subdomains in the exact same way that approved domains like do, in that they issue a unique subdomain for every independent entity. The comments even show that they have done their research before requesting to be added, but this was not enough to get approval. Reading this thread shows that no matter what, applicants that cite Facebook Marketing are going to get denied. Surely anyone reading this can see how this can be a problem. There may be thousands of businesses out there that were operating their domain and subdomains in a way where they should have listed themselves on the PSL, and now that the IOS changes have come out, that information is coming to light for them. There are lots of people out there that just realized the PSL even existed, and I think we should all take a step back to appreciate that fact. If a business has both good reason to be on the PSL not related to marketing and are making it a priority due to the IOS changes, why shouldn't they be honest about that fact?  

Another thing I am noticing throughout the comments is that sometimes a the size of a company is coming up as a point of relevance, which is not in the instructions at all. What difference should it make if someone is serving 10 businesses or 10 million?  If someone wants to create a small ticketing platform, and issue subdomains, why does their size matter? Specifically, I saw comments related to the number of subdomains under the domain. Not everyone can be the size of Shopify, and a lot of people around the world are skilling up to these issues. I realize that sometimes this is asked to gauge the level of thought the business has put into getting on the list, but I am still not a fan of that being part of the discussion. I'm not going to pretend I know every nuance here, but I believe an onlooker can see my frustration with IOS being added as an automatic wonfix rule [1245] simply to reduce volume, even if applicants fit the other criteria. I'm betting the PSL has anticipated discussions like this one, but I plea that they consider the other criteria before rejecting Facebook Marketing applicants. 


Facebook has updated their help articles to mainly reflect the corrections asked for in the GitHub comments, and even added their own form where they can help filter businesses out of applying to the PSL. This takes a lot of burden away from the PSL, but only time will tell if this method is truly effective. At the end of the day, if a business ends up at the contact form that Facebook created, they are very likely doing it to circumvent the IOS updates. Businesses that are careful about how they word their application have a chance of getting through, but as of 5/27/21 we heavily advise not citing IOS or Facebook at all if you are a platform that truly needs to get on the list, even if Facebook Marketing is a huge factor in your decision to get listed. As long as you plan on using the domain as outlined by the PSL, I really don't see why the IOS update has to come up at all. That's just what's causing the urgency but you fit the criteria all along. 

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