How to Fix the “Failed to Read the CSSRules Property From CSSStyleSheet” Error

Avoid this issue when working with style sheets in your web app

Photo by Graham Ruttan on Unsplash.

Recently, a few customers ran into a problem in an Angular web application where an exception was thrown. Because of this problem, you couldn’t use a major part of the application. As a developer, I want to have clear instructions on how to reproduce an issue to not waste time. Good customer support or customers willing to share more details beyond “It isn’t working for me” can provide meaningful information to make the life of developers easier. Customer support wasn’t able to reproduce the issue on their devices, yet it was consistently happening for a few customers.

When this issue was brought up, I did what I typically do when encountering issues like this. This article is about this particular problem as well as debugging critical issues.

Finding the Root Cause

• I used Instana, which is a great SaaS for monitoring microservices and websites. Through our monitoring tool, I was able to confirm that the error occurred for a few customers as well as the user actions that led to the issue. Even with this information, I couldn’t reproduce the issue at first.
• I had the error stack trace thanks…