“Does Blocking CSS Files in robots.txt Cause Any Issues?” Google Answers

Yes, blocking CSS files can be an issue, because they determine your layout, which can determine mobile friendliness.
SIA Team
November 4, 2021

Yesterday (November 3rd, 2021), Google released a 2-minute, 11-second video titled SEO Lightning Round 2. I presume the word lightning refers to the video’s rapid succession (and answering) of the 4 questions that were addressed. 

The video featured Google Search Advocate John Mueller, who read and quickly addressed these questions–all of which had short, straight-to-the-point answers. 

The first question was about mobile-friendliness, and asked:

“When we block CSS files on the CDN through robots.txt, the report on mobile-friendliness in Google Search Console is red. Would this affect the actual ranking?”

John’s response was:

“The short answer is, yes, it can cause issues, and you should avoid doing that. Being able to see a page completely helps us to better understand the page and confirm that it’s mobile-friendly.” 

Source: Google Search Central YouTube channel