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An avid user of strict privacy blockers myself, I have long been advocating that every web developer should test their websites in scenarios with blocked third-party resources (I can’t even count the number of times I run into websites where some functionalities don’t work because a failed ping to Google Analytics causes a UI script to fail).
Anselm Hannemann took the inspiration from Facebook’s mandatory “slow internet” Tuesdays and experimented with using Firefox’s latest privacy blocking feature for this purpose:
You might have heard that Facebook has introduced 2G Tuesdays to make developers aware of the performance implications. We can do this in many more occasions, one of them is emulating package loss with mobile data, another one ad-blocking. And as ad-blocking and privacy-extensions are on a quick rise currently with native solutions coming up as well, we should consider this a common use-case for our products we build.
Out of his five key findings, these two are the most important in my opinion:
- Always test if a variable exists, and if not, don’t let it break your entire JavaScript. Especially when your app is relying on JavaScript.
- Never (ever!) rely on the availability of any third-party (also not on an external CDN). Your app should work without it and you should have a backup plan when a 3rd party you rely on is not available.
And while at it, you might even reconsider whether leaking visitor data to certain third parties is something your visitors like anyway?
