问题
According to the Internet Assigned Numbers Authority (IANA), all .ico file falls under the MIME type image/vnd.microsoft.icon. (Source)
E.g.
<link rel="icon" type="image/vnd.microsoft.icon" href="favicon.ico" />
However, savvy internet guru, Paul Irish, claims this is wrong, and that it would actually be image/x-icon. (Source)
E.g.
<link rel="icon" type="image/x-icon" href="favicon.ico" />
I know you can get away with not including a "type" for .ico files, but if you were going to include one, which should it be? Are there actually any problems with serving it as official IANA type?
回答1:
When you're serving an .ico file to be used as a favicon, it doesn't matter. All major browsers recognize both mime types correctly. So you could put:
<!-- IE -->
<link rel="shortcut icon" type="image/x-icon" href="favicon.ico" />
<!-- other browsers -->
<link rel="icon" type="image/x-icon" href="favicon.ico" />
or the same with image/vnd.microsoft.icon, and it will work with all browsers.
Note: There is no IANA specification for the MIME-type image/x-icon, so it does appear that it is a little more unofficial than image/vnd.microsoft.icon.
The only case in which there is a difference is if you were trying to use an .ico file in an <img> tag (which is pretty unusual).
Based on previous testing, some browsers would only display .ico files as images when they were served with the MIME-type image/x-icon. More recent tests show: Chromium, Firefox and Edge are fine with both content types, IE11 is not. If you can, just avoid using ico files as images, use png.
回答2:
I think the root for this confusion is well explained in this wikipedia article.
While the IANA-registered MIME type for ICO files is image/vnd.microsoft.icon, it was submitted to IANA in 2003 by a third party and is not recognised by Microsoft software, which uses image/x-icon instead.
If even the inventor of the ICO format does not use the official MIME type, I will use image/x-icon, too.
回答3:
I have noticed that when using type="image/vnd.microsoft.icon", the favicon fails to appear when the browser is not connected to the internet.
But type="image/x-icon" works whether the browser can connect to the internet, or not.
When developing, at times I am not connected to the internet.
来源：https://stackoverflow.com/questions/13827325/correct-mime-type-for-favicon-ico