Correct MIME Type for favicon.ico?

165
votes

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?

3
htmlbrowsermime-typesfavicon
Note of caution: favicon.ico files might not be true ".ico" files. My corporate site uses a png (named "favicon.ico") and serves it with the "image/png" type. Serving it with either of the ".ico" types mentioned here were BOTH wrong, as it caused the browser to misinterpret! – Dan H

3 Answers

203
votes

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.

38
votes

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.

5
votes

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.