Does a favicon have to be 32×32 or 16×16?
Update for 2020: Sticking to the original question of 16x16 versus 32x32 icons: the current recommendation should be to provide a 32x32 icon, skipping 16x16 entirely. All current browsers and devices support 32x32 icons. The icon will routinely be upscaled to as much as 192x192 depending on the environment (assuming there are no larger sizes available or the system didn't recognize them). Upscaling from ultra low resolution has a noticeable effect so better stick to 32x32 as the smallest baseline.
For IE, Microsoft recommends 16x16, 32x32 and 48x48 packed in the favicon.ico file.
For iOS, Apple recommends specific file names and resolutions, at most 180x180 for latest devices running iOS 8.
Android Chrome primarily uses a manifest and also relies on the Apple touch icon.
IE 10 on Windows 8.0 requires PNG pictures and a background color and IE 11 on Windows 8.1 and 10 accepts several PNG pictures declared in a dedicated XML file called browserconfig.xml.
Safari for Mac OS X El Capitan introduces an SVG icon for pinned tabs.
Some other platforms look for PNG files with various resolutions, like the 96x96 picture for Google TV or the 228x228 picture for Opera Coast.
Look at this favicon pictures list for a complete reference.
TLDR: This favicon generator can generate all these files at once. The generator can also be implemented as a WordPress plugin. Full disclosure: I am the author of this site.
Short answer
The favicon is supposed to be a set of 16x16, 32x32 and 48x48 pictures in ICO format. ICO format is different than PNG. Non-square pictures are not supported.
To generate the favicon, for many reasons explained below, I advise you to use this favicon generator. Full disclosure: I'm the author of this site.
Long, comprehensive answer
Favicon must be square. Desktop browsers and Apple iOS do not support non-square icons.
The favicon is supported by several files:
- A
favicon.icoicon. - Some other PNG icons.
In order to get the best results across desktop browsers (Windows/IE, MacOS/Safari, etc.), you need to combine both types of icons.
favicon.ico
Although all desktop browsers can deal with this icon, it is primarily for older version of IE.
The ICO format is different of the PNG format. This point is tricky because some browsers are smart enough to process a PNG picture correctly, even when it was wrongly renamed with an ICO extension.
An ICO file can contain several pictures and Microsoft recommends to put 16x16, 32x32 and 48x48 versions of the icon in favicon.ico.
For example, IE will use the 16x16 version for the address bar, and the 32x32 for a task bar shortcut.
Declare the favicon with:
<link rel="icon" href="/path/to/icons/favicon.ico">
However, it is recommended to place favicon.ico in the root directory of the web site and to not declare it at all and let the modern browsers pick the PNG icons.
PNG icons
Modern desktop browsers (IE11, recent versions of Chrome, Firefox...) prefer to use PNG icons. The usual expected sizes are 16x16, 32x32 and "as big as possible". For example, MacOS/Safari uses the 196x196 icon if it is the biggest it can find.
What are the recommended sizes? Pick your favorite platforms:
- Most desktop browsers: 16x16, 32x32, "as big as possible"
- Android Chrome: 192x192
- Google TV: 96x96
- ... and others that are more or less documented.
The PNG icons are declared with:
<link rel="icon" type="image/png" href="/path/to/icons/favicon-16x16.png" sizes="16x16">
<link rel="icon" type="image/png" href="/path/to/icons/favicon-32x32.png" sizes="32x32">
...
Beware: Firefox does not support the edit: fixed in 2016.sizes attribute and uses the last PNG icon it finds. Make sure to declare the 32x32 picture last: it is good enough for Firefox, and that will prevent it from downloading a big picture it does not need.
Also note that Chrome does not support the edit: fixed in 2018.sizes attribute and tends to load all declared icons. Better not declare too many icons.
Mobile platforms
This question is about desktop favicon so there is no need to delve too much in this topic.
Apple defines touch icon for the iOS platform. iOS does not support non-square icon. It simply rescales non-square pictures to make them square (look for the Kioskea example).
Android Chrome relies on the Apple touch icon and also defines a 192x192 PNG icon.
Microsoft defines the tile picture and the browserconfig.xml file.
Conclusion
Generating a favicon that works everywhere is quite complex. I advise you to use this favicon generator. Full disclosure: I'm the author of this site.
I don't see any up to date info listed here, so here goes:
To answer this question now, 2 favicons will not do it if you want your icon to look great everywhere. See the sizes below:
16 x 16 – Standard size for browsers
24 x 24 – IE9 pinned site size for user interface
32 x 32 – IE new page tab, Windows 7+ taskbar button, Safari Reading List sidebar
48 x 48 – Windows site
57 x 57 – iPod touch, iPhone up to 3G
60 x 60 – iPhone touch up to iOS7
64 x 64 – Windows site, Safari Reader List sidebar in HiDPI/Retina
70 x 70 – Win 8.1 Metro tile
72 x 72 – iPad touch up to iOS6
76 x 76 – iOS7
96 x 96 – GoogleTV
114 x 114 – iPhone retina touch up to iOS6
120 x 120 – iPhone retina touch iOS7
128 x 128 – Chrome Web Store app, Android
144 x 144 – IE10 Metro tile for pinned site, iPad retina up to iOS6
150 x 150 – Win 8.1 Metro tile
152 x 152 – iPad retina touch iOS7
196 x 196 – Android Chrome
310 x 150 – Win 8.1 wide Metro tile
310 x 310 – Win 8.1 Metro tile
16x16 pixels, *.ico format.
2021 standards thanks to faviconit
I use faviconit.com for the best browser and device support possible. You upload an image and this site gives you the code, the converted images and a browserconfig file.
We could simply upload a favicon manually to our website of 16x16 and it will probably show up in almost any browser.
But when you will mark it as one of your favorites on your smartphone or tablet, we will need larger images (60x60 to 144x144).
And lets say one of our users creates a shortcut on their desktop. In that case a 196x196 looks better!
Example code of what faviconit would give you, next to all the converted images:
<!-- place this in your <head></head> -->
<link rel="shortcut icon" href="/favicon.ico">
<link rel="icon" sizes="16x16 32x32 64x64" href="/favicon.ico">
<link rel="icon" type="image/png" sizes="196x196" href="/favicon-192.png">
<link rel="icon" type="image/png" sizes="160x160" href="/favicon-160.png">
<link rel="icon" type="image/png" sizes="96x96" href="/favicon-96.png">
<link rel="icon" type="image/png" sizes="64x64" href="/favicon-64.png">
<link rel="icon" type="image/png" sizes="32x32" href="/favicon-32.png">
<link rel="icon" type="image/png" sizes="16x16" href="/favicon-16.png">
<link rel="apple-touch-icon" href="/favicon-57.png">
<link rel="apple-touch-icon" sizes="114x114" href="/favicon-114.png">
<link rel="apple-touch-icon" sizes="72x72" href="/favicon-72.png">
<link rel="apple-touch-icon" sizes="144x144" href="/favicon-144.png">
<link rel="apple-touch-icon" sizes="60x60" href="/favicon-60.png">
<link rel="apple-touch-icon" sizes="120x120" href="/favicon-120.png">
<link rel="apple-touch-icon" sizes="76x76" href="/favicon-76.png">
<link rel="apple-touch-icon" sizes="152x152" href="/favicon-152.png">
<link rel="apple-touch-icon" sizes="180x180" href="/favicon-180.png">
Since Windows 8
But that is not all. Since windows 8 we are able to create shortcuts to websites with tiles!
<!-- place this in your <head></head> -->
<meta name="msapplication-TileColor" content="#FFFFFF">
<meta name="msapplication-TileImage" content="/favicon-144.png">
<meta name="msapplication-config" content="/browserconfig.xml">
Browserconfig.xml
Upload a file named browserconfig.xml (to enable the tiles in windows >8)
<browserconfig>
<msapplication>
<tile>
<square70x70logo src="/favicon-70.png"/>
<square150x150logo src="/favicon-150.png"/>
<square310x310logo src="/favicon-310.png"/>
<TileColor>#FFFFFF</TileColor>
</tile>
</msapplication>
</browserconfig>