How to save up another precious HTTP-request for the tiny favicon?
Solution 1:
I think for the most part it does not result in another HTTP request as these are usually dumped in the browser's cache after the first access.
This is actually more efficient than any of the proposed "solutions".
Solution 2:
A minor improvement to @yc's answer is injecting the Base64-encoded favicon from a JavaScript file that would normally be used and cached anyway, and also suppressing the standard browser behavior of requesting favicon.ico by feeding it a data URI in the relevant meta tag.
This technique avoids the extra http request and is confirmed to work in recent versions of Chrome, Firefox and Opera on Windows 7. However it doesn't appear to work in Internet Explorer 9 at least.
File index.html
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<!-- Suppress browser request for favicon.ico -->
<link rel="shortcut icon"type="image/x-icon" href="data:image/x-icon;,">
<script src="script.js"></script>
...
File script.js
var favIcon = "\
iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAABrUlEQVR42mNkwAOepOgxMTD9mwhk\
[...truncated for brevity...]
IALgNIBUQBUDAFi2whGNUZ3eAAAAAElFTkSuQmCC";
var docHead = document.getElementsByTagName('head')[0];
var newLink = document.createElement('link');
newLink.rel = 'shortcut icon';
newLink.href = 'data:image/png;base64,'+favIcon;
docHead.appendChild(newLink);
/* Other JavaScript code would normally be in here too. */
Demo: turi.co/up/favicon.html
Solution 3:
You could try a data URI. No HTTP request!
<link id="favicon" rel="shortcut icon" type="image/png" href="data:image/png;base64,....==">
Unless your pages have static caching, your favicon wouldn't be able to be cached, and depending on the size of your favicon image, your source code could get kind of bloated as a result.
Data URI favicons seems to work in most modern browsers; I have it working in recent versions of Chrome, Firefox and Safari on a Mac. Doesn't seem to work in Internet Explorer, and possibly some versions of Opera.
If you're worried about old Internet Explorer versions (and you probably shouldn't be these days), you could include an Internet Explorer conditional comment that would load the actual favicon.ico in the traditional way, since it seems that older Internet Explorer doesn't support data URI favicons.
`<!--[if IE ]><link rel="shortcut icon" href="http://example.com/favicon.ico" type="image/x-icon" /><![endif]--> `
- Include the favicon.ico file in your root directory to cover browsers that will request it either way, since for those browsers, if they're already checking no matter what you do, you might as well not waste the HTTP request with a 404 response.
You could also just use the favicon of another popular site which is likely to have their favicon cached, like http://google.com/favicon.ico, so that it is served from cache.
As commenters have pointed out, just because you can do this doesn't mean you should, since some browsers will request favicon.ico regardless of the tricks we devise. The amount of overhead you'd save by doing this would be minuscule compared to the savings you'd get from doing things like gzipping, using far-future expires headers for static content, minifying JavaScript files, putting background images into sprites or data URIs, serving static files off of a CDN, etc.
Solution 4:
Killer Solution in 2020
This solution necessarily comes nine years after the question was originally asked, because, until fairly recently, most browsers have not been able to handle favicons in .svg format.
That's not the case anymore.
See: https://caniuse.com/#feat=link-icon-svg
1) Choose SVG as the Favicon format
Right now, in June 2020, these browsers can handle SVG Favicons:
- Chrome
- Firefox
- Edge
- Opera
- Chrome for Android
- KaiOS Browser
Note that these browsers still can't:
- Safari
- iOS Safari
- Firefox for Android
Nevertheless, with the above in mind, we can now use SVG Favicons with a reasonable degree of confidence.
2) Present the SVG as a Data URL
The main objective here is to avoid HTTP Requests.
As other solutions on this page have mentioned, a pretty smart way to do this is to use a Data URL rather than an HTTP URL.
SVGs (especially small SVGs) lend themselves perfectly to Data URLs, because the latter is simply plaintext (with any potentially ambiguous characters percentage-encoded) and the former, being XML, can be written out as a long line of plaintext (with a smattering of percentage codes) incredibly straightforwardly.
3) The entire SVG is a single Emoji
N.B. This step is optional. Your SVG can be a single emoji, but it can just as easily be a more complex SVG.
In December 2019, Leandro Linares was one of the first to realise that since Chrome had joined Firefox in supporting SVG Favicons, it was worth experimenting to see if a favicon could be created out of an emoji:
https://lean8086.com/articles/using-an-emoji-as-favicon-with-svg/
Linares' hunch was right.
Several months later (March 2020), Code Pirate Lea Verou realised the same thing:
https://twitter.com/leaverou/status/1241619866475474946
And favicons were never the same again.
4) Implementing the solution yourself:
Here's a simple SVG:
<svg
xmlns="http://www.w3.org/2000/svg"
viewBox="0 0 16 16">
<text x="0" y="14">🦄</text>
</svg>
And here's the same SVG as a Data URL:
data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%2016%2016'%3E%3Ctext%20x='0'%20y='14'%3E🦄%3C/text%3E%3C/svg%3E
And, finally, here's that Data URL as a Favicon:
<link rel="icon" href="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%2016%2016'%3E%3Ctext%20x='0'%20y='14'%3E🦄%3C/text%3E%3C/svg%3E" type="image/svg+xml" />
5) More tricks (...these are not your parents' favicons!)
Since the Favicon is an SVG, any number of filter effects (both SVG and CSS) can be applied to it.
For instance, alongside the White Unicorn Favicon above, we can easily make a Black Unicorn Favicon by applying the filter:
style="filter: invert(100%);"
Black Unicorn Favicon:
<link rel="icon" href="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%2016%2016'%3E%3Ctext%20x='0'%20y='14'%20style='filter:%20invert(100%);'%3E🦄%3C/text%3E%3C/svg%3E" type="image/svg+xml" />
Solution 5:
You could use a Base64-encoded favicon, like:
<link href="data:image/x-icon;base64,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" rel="icon" type="image/x-icon" />