In June, it was revealed that Safari in iOS9 would support ad blocking. Last week, ad blocking on iOS became a reality.

This week, the iOS ad blocking apocalypse is in full swing and the victims aren’t just companies that rely on digital advertising to generate revenue.

As detailed by Fortune, the most popular iOS ad blocker, Crystal, is currently preventing a number of high-profile ecommerce sites from rendering. Retailers affected include Walmart, Sears, Walgreens and Lululemon.

Last Cyber Monday 78% of mobile shopping took place on iOS devices and according to Chris Mason the CEO of Branding Brand the implications of ad blocking could be significant this holiday shopping season…

First, the experience for customers will be lessened. Lots of sites will be missing content, have broken links or customers won’t be able to add certain items to their shopping carts. They’ll probably just think the site is broken, but it’s really their content blocker. Second, retailers will be data-blind, or at least data-dark. It will really impact their ability to make quick judgments.

The magnitude of the problem can be significant. In Fortune’s tests, pages on Sears.com and Walgreens.com literally went blank with Crystal installed. Other websites, like Walmart.com, appeared functional, but Crystal prevented users from actually adding products to cart, a big problem to say the least.

Crystal’s creator, Dan Murphy, is making changes as the problems associated with his app make headlines, but even after he said he had addressed issues affecting certain retailer sites, Fortune encountered new problems with some of them. 

99 problems, but an ad blocker isn’t one?

Even websites that remain fully functional from an end user perspective don’t necessarily escape unscathed. As Fortune’s Dan Primack notes,

Even for mobile websites that are working properly from a customer perspective, such ad-blocking technology also can strip out back-end code like Google Analytics or Adobe’s Omniture, which provide retailers with real-time insights into customer behavior. And then there is the whole matter of how retailers generate around 60% of their mobile web traffic inorganically, via online ads that Crystal and other ad-blockers are designed to eliminate.

Put simply, lots and lots of companies are going to be impacted in some way by ad blocking in Safari on iOS. So how can they deal with it? Unfortunately, it’s complicated.

In some cases, the most reliable workaround is to ditch certain third-party services that ad blockers frequently target, but doing this can often be technically complex or costly to do. Another approach that might be viable for larger companies is to reach out to the creators of popular ad blockers directly.

A new testing paradigm

Ultimately, it appears that just as companies that are serious about the web have learned to do thorough cross-browser and cross-device testing to ensure that their experiences work everywhere, companies may be forced to do thorough testing of their websites using ad blockers. 

Right now, ad blockers represent some of the most popular iOS apps in the App Store and combined have been downloaded more than 500,000 times in the first week. Popular choices include Crystal, Purify, Blockr and Weblock.

Companies interested in determining the impact of ad blockers on their mobile sites will want to test their mobile sites using most or all of these apps. They’ll also want to monitor as they are updated, and new apps gain in popularity.

No turning back

Despite the chaos created by Safari’s new support for ad blocking, companies shouldn’t expect Apple to reverse course. Consumer distaste for online ads has reached a boiling point and Apple isn’t going lose any consumer friends helping iOS users block ads on their tablets and mobile phones.

As for enemies, as some have noted, one of Apple’s arch rivals, Google, derives most of its revenue from online ads, giving Apple another incentive for facilitating ad blocking on its devices.

Unfortunately, there is collateral damage here and all companies active on the mobile web will need to learn to live in a world where iOS users have ad blockers.