This is how I have set up the icon-links in my header.
<link rel="shortcut icon" type="image/x-icon" href="favicon.ico" />
<link rel="apple-touch-icon" href="apple-touch-icon.png">
<link rel="icon" type="image/png" href="/screen/favicon.png" sizes="192x192">
My 16x16 favicon.ico shows a simplified version of my logo, which looks much better than a downscaled version of a larger PNG. For the touch-icons on mobile devices I have created a 192x192 png of my original logo. Since I added that larger PNG to my header, it is not only used (correctly) as a touch-icon, but also replaces the 16x16 favicon.ico. Thus on the browsers the downscaled png-version is display. I dislike it, cause the ico-version looks better.
Is there any way, to force the display of the ico-version of my favicon in browsers?
If the reason of your high-resolution image/png icon is Android, then you should declare it via a web manifest.
This is what RealFaviconGenerator does: it only declares low-resolution image/png icons in the HTML. So desktop browsers only pick those, whereas Android get the high resolution icons it expects. Even if you don't plan to use the service, you can generate a fake set of icons and adapt the generated code and files to your needs.
Full disclosure: I'm the author of this service.
This question already has answers here:
What is the best practice for creating a favicon on a web site? [closed]
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What favicon dimensions, file formats and meta/link tags should be used as of 2022? This includes apple icon, windows, android and other devices people use today.
I use Opera and I can see it supports svg format. Is it the best solution to use svg nowadays? Is there any option "one file fits all"?
I've been browsing many websites and checked different "favicon generators". All of them are years old and work mostly with png files.
For example:
What code should be used for ico and svg?
<link rel="icon" href="favicon.ico" type="image/ico">
<link rel="icon" href="favicon.svg" type="image/svg+xml">
or should dimensions be specified if ico contains more sizes? I didn't find one good answer.
<link rel="icon" sizes="16x16 24x24 32x32 48x48 64x64" href="favicon.ico">
Please provide dimensions, file formats and meta/link tags of what favicons should be used.
Disclaimer: I'm the author of RealFaviconGenerator, which I expect to be up-to-date (mostly, see below). So don't be surprised if this answer matches what RFG generates.
The one-size-fits-all myth
There is no "one size fits all" icon. You can't create a single SVG icon and expect it to work everywhere.
From a technical point of view, a single SVG icon would be a good thing. But from a UI and UX point of view, this is not a desirable outcome. Compare iOS and Android. On iOS, all home screen icons are squares with rounded corners (iOS fills transparent regions of Touch icons with black). On Android, home screen icons often use non-square shapes and transparency (including Google app icons). Submit a single touch icon and Android Chrome will use it. But you won't be able to match Android icon guidelines, whereas a dedicated icon could.
So I advice to deliberately avoid using a single icon. Rather target each platform individually, when possible (this is not always the case).
Icons, platform per platform
iOS Safari
iOS Safari expects a touch icon. As of today, this is a 180x180 PNG image. This image should not use transparency and its corners will be automatically rounded when added to home screen. Declared with:
<link rel="apple-touch-icon" sizes="180x180" href="/icons/apple-touch-icon.png">
Over the years, this icon has become the "default high resolution icon" for many browsers. So you will find it elsewhere, when adding to bookmark, etc.
Android Chrome
Android Chrome relies on the Web App Manifest. Although this manifest is not dedicated to Android Chrome, it is currently its main supporter. So at the moment, it is still quite safe to consider the icons from the Web App Manifest to be for Android Chrome.
As the name suggests, the Web App Manifest is for, well, web apps. But any web site can use it as a way to reference some icons.
Android expects a 192x192 PNG icon, transparency allowed and encouraged.
The manifest is declared with:
<link rel="manifest" href="/icons/site.webmanifest">
Edge and IE 12
Microsoft introduced the browserconfig, an XML document which lists various icons that fit the Metro UI.
The file and background color are declared with:
<meta name="msapplication-TileColor" content="#da532c">
<meta name="msapplication-config" content="/icons/browserconfig.xml">
Classic desktop browsers
Windows/macOS Chrome, Windows/macOS Firefox, Safari, IE... This is were things are a little more blurry. Historically, there was a single favicon.ico file, still supported. However, most recent browsers rather pick PNG icons, which are lighter. Plus some browsers are not able to select the proper icon in the ICO file (this format can embed several versions of an icon), leading a low resolution icon being wrongly used.
One could be tempted to drop the old favicon.ico entirely. Although I would like to make this leap in RFG, I didn't run the necessary tests to evaluate the impact on the old browsers.
Thus the combo I still recommend today, with favicon.ico embedding 16x16, 32x32 and 48x48 icons:
<link rel="icon" type="image/png" sizes="32x32" href="/icons/favicon-32x32.png">
<link rel="icon" type="image/png" sizes="16x16" href="/icons/favicon-16x16.png">
<link rel="shortcut icon" href="/icons/favicon.ico">
Other browsers
Other browsers may have dedicated icons. For example Coast by Opera is looking for a 228x228 icon. The need to focus on these browsers is not obvious. They usually use the touch icon or other icons when they cannot find "their" icon.
Conclusion
As announced at the beginning, this is exactly what RealFaviconGenerator creates.
It is also worth mentioning that together with favicon some other tags should be added like OG tags, Twitter cards or MS-application. It all serves the same purpose - visual identification of your brand and should also be included.
Twitter card can be found HERE
I add following tags
<meta name="twitter:card" content="summary_large_image">
<meta name="twitter:site" content="#YourAccount">
<meta name="twitter:creator" content="#YourAccount">
<meta name="twitter:title" content="Title of your page">
<meta name="twitter:url" content="URL of your page">
<meta name="twitter:description" content="Your description here">
<meta name="twitter:image:src" content="URL of image">
I found that many users make images 1300px by 650px and jpg/png formats.
After adding all tags they should be validated HERE
Facebook OG has more option but general are as follows:
<meta property="og:title" content="ENTER PAGE TITLE">
<meta property="og:type" content="website"><!--Different values possible -->
<meta property="og:url" content="ENTER PAGE URL">
<meta property="og:image" content="URL OF IMAGE">
<meta property="og:image:width" content="1240">
<meta property="og:image:height" content="650">
<meta property="og:site_name" content="ENTER YOUR SITE NAME">
<meta property="og:description" content="ENTER YOUR PAGE DESCRIPTION">
<meta property="fb:app_id" content="ENTER YOUR FB APP ID">
<meta property="og:see_also" content="URL to recommended page number 1">
<meta property="og:see_also" content="URL to recommended page number 2">
<!--UP TO 5 WEBSITE ADRESSES -->
Facebook recommend specific ratio of the image and the file size is limited to 8Mb. To keep similar images with twitter card I recommend dimensions 1240px by 650px and jpg/png format. Facebook and twitter do not accept svg...
I found that some global brands use this tag on their websites. One had dimensions 150x150 pixels and png format. This image may be used by browsers to display in search results.
<meta name="thumbnail" content="path/to/image/thumb-150x150.png">
Real Favicon Generator covers also Microsoft favicons. There are many other meta tags for MS-application to optimize bow the page and other infos such as image are displayed. This topic is also worth reading.
I hope this is usefull for someone and expands the topic of branding your website.
I had the exact same question a few weeks back. It is surprisingly hard to find reliable up-to-date information about favicons on the internet. In fact MDN and W3C both link to Wikipedia for more info about favicons. The Wikipedia article, however, is quite short and not very helpful. It took me several hours to research what the optimal icons for modern browsers are.
This is what I learnt:
There is no "one file to rule them all" solution. However, for modern browsers, it is actually not that much you need.
The standard favicon size in browsers is still 16x16 points corresponding to 32x32 pixels on high resolution screens.
There is no need to still include a favicon.ico file in your root directory unless you want to support IE 10 or older.
SVG would be nice, but is not supported by all browsers. So the easiest solution is still to just use PNG images.
Google explicitly says they don't support 16x16 or 32x32 icons. For Google results, you need to include at least one icon that is a multiple of 48x48.
For when users pin your website on their phone's launch screen you need a 192x192 icon for Android, 167x167 for iPad and 180x180 for iPhone (while the link tags for iPhone are special — see below)
In theory, you could provide a single 192x192 (or higher multiple of 48) icon which would be scaled down by browsers and all other services, but especially for the 16x16 point version, these scaling results will probably be worse than what you get when you scale it yourself with a professional image editor or even provide special versions for these low resolution icons.
You can also add a web manifest file that includes more meta info like theme colors. But that is only supported on Android and brings little benefit unless you really expect a large share of your users to pin your website on their home screen (in my humble opinion that is very unlikely for most websites).
My recommendation would be to use the following in your header:
<!-- For all browsers -->
<link rel="icon" type="image/png" sizes="32x32" href="favicon-32x32.png">
<link rel="icon" type="image/png" sizes="16x16" href="favicon-16x16.png">
<!-- For Google and Android -->
<link rel="icon" type="image/png" sizes="48x48" href="favicon-48x48.png">
<link rel="icon" type="image/png" sizes="192x192" href="favicon-192x192.png">
<!-- For iPad -->
<link rel="apple-touch-icon" type="image/png" sizes="167x167" href="favicon-167x167.png">
<!-- For iPhone -->
<link rel="apple-touch-icon" type="image/png" sizes="180x180" href="favicon-180x180.png">
I have also written a blog post with a bit more prose and more background information.
After going through the page source, I found:
<link rel="apple-touch-icon image_src" href="//cdn.sstatic.net/stackoverflow/img/apple-touch-icon.png?v=41f6e13ade69">
But even after I did that, my image still has a bored effect. My image is also a transparent png. Any ideas?
Here is my attempt (10.10.1 OS X Yosemite, Safari: Version 8.0.2):
I used this website to generate the favico:
http://realfavicongenerator.net
<link rel="apple-touch-icon" sizes="57x57" href="/apple-touch-icon-57x57.png">
<link rel="apple-touch-icon" sizes="114x114" href="/apple-touch-icon-114x114.png">
<link rel="apple-touch-icon" sizes="72x72" href="/apple-touch-icon-72x72.png">
<link rel="apple-touch-icon" sizes="144x144" href="/apple-touch-icon-144x144.png">
<link rel="apple-touch-icon" sizes="60x60" href="/apple-touch-icon-60x60.png">
<link rel="apple-touch-icon" sizes="120x120" href="/apple-touch-icon-120x120.png">
<link rel="apple-touch-icon" sizes="76x76" href="/apple-touch-icon-76x76.png">
<link rel="apple-touch-icon" sizes="152x152" href="/apple-touch-icon-152x152.png">
<link rel="icon" type="image/png" href="/favicon-96x96.png" sizes="96x96">
<link rel="icon" type="image/png" href="/favicon-16x16.png" sizes="16x16">
<link rel="icon" type="image/png" href="/favicon-32x32.png" sizes="32x32">
<meta name="msapplication-TileColor" content="#da532c">
<meta name="msapplication-TileImage" content="/mstile-144x144.png">
Two things in this answer:
How I did to reproduce StackOverflow's behavior
Why this may not be a good idea
How to reproduce StackOverflow's behavior
What I did:
Download http:////cdn.sstatic.net/stackoverflow/img/apple-touch-icon.png
Submit this picture to RealFaviconGenerator (full disclosure: I'm the author of this site)
Put the generated pics and HTML in a test web site
Access it with Safari and add a bookmark
I got your expected result, ie. a transparent background.
This is basically what you did, so there must be something wrong. A few tips:
There can be a lot of issues with favicon, whatever the browser. They often cache the old icon and do not load the new one. Sometimes they do not load your icon at all, but load it if you wait a few seconds. And so on. My advice: try to use another domain to make sure you start from a fresh state.
Maybe your test web site as some additional stuff that can conflict with your actual test. For example, if you have a file apple-touch-icon.png in your root directory, Safari may load it, even if it is not declared in your HTML code.
Why this may not be a good idea
Mac OS Safari relies on the Touch icon, primarily designed for iOS. It is mainly used for the "Add to home screen" feature. In that case, iOS prevents transparency and fills transparent regions with black. Add StackOverflow.com to the home screen and you get:
Honestly the result is okay, but is this really what SO expected? Your choice.
I figured out the problem here.
The farthest one on the right has a TLD of .io
The center one has a TLD of .com
They are exact clones, the same code on. So it must be because the domain TLD is not .com/.net
Edit:
To further recap information I found about this. It seems like adding a www in front of my domain, allows it to be fully transparent.
mysite.com works
www.mysite.com works
mysite.io doesn't work
www.mysite.io works
Transparent Apple Touch icons are indeed possible. What you need to do is strip all excess information from the PNG using ImageOptim for Mac or a similar program on Windows. I did extensive research and stumbled on the answer by looking at the Apple Touch icon used by the Virtual DJ site. This icon keeps its transparent background on iOS and MacOS Sierra. I looked at the file size and realized how small it was compared to the custom apple touch icons with transparency that I made for my favorites in Safari. Next I looked at the file information using the inspector in Mac's Preview app. All of my custom apple touch icons had four tabs in the inspector section named General, exif, PNG and TIFF. The virtual DJ icon only had two tabs named PNG and General. Once I ran my custom images through ImageOptim the file sizes plummeted by over 90% and the extra TIFF and exif tabs disappeared from the inspector in Preview. Sure enough once I reloaded my custom images and launched Safari all of my Favorites tabs have transparent backgrounds!
<link rel="shortcut icon" href="/favicon.ico">
<link rel="Bookmark" href="/favicon.ico">
I saw it somewhere,but is <link rel="Bookmark".. necessary?
That bookmark link is incorrect. It should be:
<link rel="bookmark" href="http://my.site.com/some/path/permalink.html">
ie a perma-link and not the icon. See 6.12 Link types from the HTML 4.01 specification:
Bookmark Refers to a bookmark. A bookmark is a link to a key entry
point within an extended document. The
title attribute may be used, for
example, to label the bookmark. Note
that several bookmarks may be defined
in each document.
This is the cross-browser way of adding favicons:
<link rel="icon" href="/favicon.ico" />
<link rel="Shortcut Icon" href="/favicon.ico" type="image/x-icon" />
the icon file itself would preferably be 16x16 pixels and in gif format (IE6 wont use transparent png) and under 500 bytes. Though most modern browsers now accept practically anything, though of course it will be your bandwidth and their waiting.
i googled for a page stating this.
link
as cletus mentions, the Bookmark link is not for favicon and the code you provided is actually wrong.
EDIT: the favicon link does not influence your bookmarking itself, yet it helps the browser store a little icon on the tabs or your browser's bookmarks' menu. StackOverflow uses this icon.
But Is It necessary? If your icon is located at /favicon.ico, no it is not absolutely critical at all. Most browsers check that path by default, but if you like me put your favicon in a directory like /images/favicon.ico you would need to tell the browser to get it from there or your server will build up alot of 404-Not Found errors in its log. Which will slow things down (a bit). Also you might want to have different icons for different directories etc.
This is a crossbrowser way to make sure the browser knows where your favicon is located for both viewing the page and bookmarking the page. Chances are, if you don't know what that code is, you don't have a favicon. The easiest way to make on is to make a 16x16px gif and change its extension to '.ico' - then you'll get your little icon in the corner of the browser bar (depending on your browser).
I'd like to use a single image as both a regular favicon and iPhone/iPad friendly favicon.
Is this possible? Would an iPad-friendly 72×72 PNG scale if linked to as a regular browser favicon? Or do I have to use a separate 16×16 or 32×32 image?
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.ico icon.
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 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. edit: fixed in 2016.
Also note that Chrome does not support the sizes attribute and tends to load all declared icons. Better not declare too many icons. edit: fixed in 2018.
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
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>
16x16 pixels, *.ico format.
I am not sure if/how browsers scale large icons, but The W3C suggests the following1:
The format for the image you have chosen must be 16x16 pixels or 32x32 pixels, using either 8-bit or 24-bit colors. The format of the image must be one of PNG (a W3C standard), GIF, or ICO.
1 w3c.org: How to Add a Favicon to your Site (Draft in development).
Actually, to make your favicon work in all browsers properly, you will have to add more than 10 files in the correct sizes and formats.
My friend and I have created an App just for this! you can find it in faviconit.com
We did this, so people don't have to create all these images and the correct tags by hand, create all of them used to annoy me a lot!
The simplest solution (2021)
Use one(!) SVG image
If you do not care about supporting Safari, you can use a single SVG icon:
<link rel="icon" href="favicon.svg" type="image/svg+xml" sizes="any">
Use one(!) PNG image
If you want full support*, you should add this to the head of your document:
<link rel="shortcut icon" type="image/png" href="/img/icon-192x192.png">
<link rel="shortcut icon" sizes="192x192" href="/img/icon-192x192.png">
<link rel="apple-touch-icon" href="/img/icon-192x192.png">
The last link is for Apple (home screen), the second one for Android (home screen) and the first one for the rest.
The size is exactly the size the Android home screen uses. The Apple home screen icon size is 60px (3x), so 180px and will be scaled down. Other platforms use the default shortcut icon, which will be scaled down too.
*Note that this solution does not support "tiles" in Windows 8/10. It does, however, support images in shortcuts, bookmarks and browser-tabs.
Wikipedia has this to say:
Additionally, such icon files can be
either 16×16 or 32×32 pixels in size,
and either 8-bit or 24-bit in color
depth (note that GIF files have a
limited, 256 color palette entries).
I think the best way is to use a 32x32 gif and test it with different browsers.
Simple solution for modern browsers (2022)
Use an SVG favicon:
<link rel="icon" href="/icon.svg">
Supported by major browsers (except Safari in 2021) and Living Standard
Only 1 short line of code and simple to remember
Other attributes like type and sizes are not necessary
Scales much better at any size compared to PNG
Let's end the favicon craziness with hundreds of different sizes...
You can have multiple sizes of icons in the same file. I routinely create favicons (.ico file) that are 48, 32, and 16 pixels. You can add in any size image you want. The question is, will the iPhone use an ico file?
ico also supports transparency, but I'm not sure if it's an alpha channel like PNG; probably more like GIF where it's on or it's off.
According to the Wikipedia Article on Favicon, Internet Explorer supports only the ICO format for favicons.
I would stick with two different icons.
As I learned, no one of those several solutions are perfects. Using a favicon generator is indeed a good solution but their number is overwhelming and it's hard to choose. I d'like to add that if you want your website to be PWA enabled, you need to provide also a 512x512 icon as stated by Google Devs :
icons including a 192px and a 512px version
I didn't met a lot of favicon generators enforcing that criteria (firebase does, but there is a lot of things it doesn't do). So the solution must be a mix of many other solutions.
I don't know, today at the begining of 2020 if providing a 16x16, 32x32 still relevant. I guess it still matters in certain context like, for example, if your users still use IE for some reason (this stills happen in some privates companies which doesn't migrate to a newer browser for some reasons)
No, you can't use a non-standard size or dimension, as it'd wreak havoc on peoples' browsers wherever the icons are displayed. You could make it 12x16 (with four pixels of white/transparent padding on the 12 pixel side) to preserve your aspect ratio, but you can't go bigger (well, you can, but the browser'll shrink it).
You will need separate files for each resolution I am afraid. There is a really good article on campaign monitor describing how they created and implemented their icons for each iOS device too:
http://www.campaignmonitor.com/blog/post/3234/designing-campaign-monitor-ios-icons/
The format of favicon must be square otherwise the browser will stretch it. Unfortunatelly, Internet Explorer < 11 do not support .gif, or .png filetypes, but only Microsoft's .ico format. You can use some "favicon generator" app like: http://favicon-generator.org/
favicon.ico is 16x16
<link rel="shortcut icon" href="favicon.ico"/>
And I use these ones to be beautiful in mobile and tablet:
<link rel="apple-touch-icon-precomposed" sizes="144x144" href="img/ico144.png">
<link rel="apple-touch-icon-precomposed" sizes="114x114" href="img/ico114.png">
<link rel="apple-touch-icon-precomposed" sizes="72x72" href="img/ico72.png">
<link rel="apple-touch-icon-precomposed" href="img/ico57.png">
It's important to use the name "favicon.ico" in the root because many browsers will try to find there first.
Seems like your file should be .ico type.
Check this post about favicons:
http://www.html-kit.com/support/favicon/image-size/
the format for the image you have chosen must be 16x16 pixels or
32x32 pixels, using either 8-bit or 24-bit colors. The format of the
image must be one of PNG (a W3C standard), GIF, or ICO. - How to Add a Favicon to your Site - QA # W3C
The favicon doesn't have to be 16x16 or 32x32. You can create a favicon that is 80x80 or 100x100, just make sure that both values are the same size, and obviously don't make it too large or too small, choose a reasonable size.
May I remind everybody that the question was:
I'd like to use a single image as both a regular favicon and iPhone/iPad friendly favicon? Is this possible? Would an iPad-friendly 72x72 PNG scale if linked to as a regular browser favicon? Or do I have to use a separate 16x16 or 32x32 image?
The answer is: YES, that is possible! YES, it will be scaled. NO, you do not need a 'regular browser favicon'. Please look at this answer: https://stackoverflow.com/a/48646940/2397550