margin-trim is only partially supported in Safari

What type of issue is this?

Incorrect support data (example: BrowserX says "86" but support was added in "40")

What information was incorrect, unhelpful, or incomplete?

Currently the margin-trim property is shown as fully supported in Safari, however it is only supported in block layout and not in multicol. The issue for implementing multicol support is https://bugs.webkit.org/show_bug.cgi?id=252325

The implementation in Chrome 155 includes support for block layout and multicol.

I can make a PR for this, I just thought I'd raise the issue while thinking about it.

What browsers does this problem apply to, if applicable?

Safari

What did you expect to see?

I think we need a line for "supported in multicol".

Did you test this? If so, how?

A quick test is here https://codepen.io/rachelandrew/pen/vYarNxq there should be no initial margin on the first paragraph inside the multicol container, if margin-trim: block-start is supported for multicol containers.

Can you link to any release notes, bugs, pull requests, or MDN pages related to this?

• https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/margin-trim#browser_compatibility
• https://bugs.webkit.org/show_bug.cgi?id=252325

Do you have anything more you want to share?

No response

MDN URL

No response

MDN metadata

No response

Start by locating the browser-compat-data entry for CSS margin-trim and review its Safari support data. Compare the block-layout and multicol behavior with WebKit bug 252325 and the linked CodePen test; done when the data distinguishes multicol support instead of marking Safari fully supported.