Is there a CSS file size limit in IE9?

Question

I was trying to research a file size limit in IE9. There are many anecdotal links about one existing (mostly 288KB limit ones), but I could not find any proper documentation on any of them. There were approximately as many people saying that it exists as people who said it does not exist.

Some links on both sides:

Thinking it exists:

• https://mitchgavan.com/style-sheet-limitations-in-ie9/
• Does IE9 have a file size limit for CSS?

Thinking it does not exist:

• https://makandracards.com/makandra/10883-limitations-you-should-be-aware-of-when-internet-explorer-9-parses-css-files
• https://spaceninja.com/2015/03/31/ie-css-limits/

The official Microsoft documentation does not state this limit, but it does not refute its existence either. I made a test file that was 1 CSS rule, a lot of white space to get it to 300KB, and then a second rule. The second rule definitely was applied. I'm still confused where this notion of this 288KB limit came from though.

Given that it is now 2018, there should be some consensus on this limit, right? Does anyone know if this limit exists or not? If it does, I'd like some kind of formal proof of it. If it doesn't, I'd at least like to know where the idea came from.

Please do not mark this as a duplicate unless you give me a link that definitively gives some source as to what this limit is, or proves that it doesn't exist.

Centripetal

Why not test it for yourself? If the limit is actually rules or selectors, then it should be trivial to create a CSS file of arbitrary size containing two rules and selectors and any amount of white space between them. If it works fine regardless of the amount of white space you put there, you'll know that there's no file size limit. – Whitworth

I did this, and it still read the whole file. I'm wondering where the idea of this rule even came from, however. – Centripetal

Maybe there's some case I'm missing, or it doesn't include whitespace? – Centripetal

Answer 1

After extensive testing and research, I have to conclude that no such limit exists for IE9. Why there are many rumors on the internet about it, I have no clue, but I could not find any official documentation of the fact. Any suggestion of this fact has just been unsupported Stack Overflow comments or random blog posts. After making my own CSS that was over 288KB, and seeing it successfully load all rules, I don't see how this limit could exist. It's possible these people were hitting the selector limit, but I can't investigate further as there are no files that exist that are over 288KB, don't hit the selector limit, and are purported to not fully load in IE9. I hope future developers can see this question, and not waste as much time on this random IE9 tidbit as I have.

Centripetal