Improved version of JavaScript fix for the iOS viewport scaling bug. See http://www.blog.highub.com/mobile-2/a-fix-for-iphone-viewport-scale-bug/

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iphone-viewport-scaling-bug-fix-original.js
JavaScript
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// Original code form http://www.blog.highub.com/mobile-2/a-fix-for-iphone-viewport-scale-bug/
 
var metas = document.getElementsByTagName('meta');
var i;
if (navigator.userAgent.match(/iPhone/i)) {
for (i=0; i<metas.length; i++) {
if (metas[i].name == "viewport") {
metas[i].content = "width=device-width, minimum-scale=1.0, maximum-scale=1.0";
}
}
document.getElementsByTagName('body')[0].addEventListener("gesturestart", gestureStart, false);
}
function gestureStart() {
for (i=0; i<metas.length; i++) {
if (metas[i].name == "viewport") {
metas[i].content = "width=device-width, minimum-scale=0.25, maximum-scale=1.6";
}
}
}
iphone-viewport-scaling-bug-fix.js
JavaScript
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// My rewritten version
(function() {
 
var metas = document.querySelectorAll('meta[name="viewport"]'),
forEach = [].forEach;
 
function fixMetas(firstTime) {
forEach.call(metas, function(el) {
el.content = firstTime
? 'width=device-width,minimum-scale=1.0,maximum-scale=1.0'
: 'width=device-width,minimum-scale=0.25,maximum-scale=1.6';
});
}
 
fixMetas(true);
 
document.body.addEventListener('gesturestart', fixMetas, false);
 
}());

Demo (try on iOS): http://mathiasbynens.be/demo/ios-viewport-scaling

Just like the original script, this snippet locks zooming by setting both minimum-scale and maximum-scale to 1.0 on load, effectively overwriting the values specified in the HTML, e.g.

<meta name="viewport" content="width=device-width,initial-scale=1.0">

By locking these values, zooming is disabled, even when the orientation of the device changes (which would normally trigger the zoom bug).

The script also accounts for the case where there are multiple meta name="viewport" elements in the HTML. I know, it should never happen — but we take care of it just in case.

This script is effectively the same as the original; only the code changed. No bugs were fixed, no features were added. Some important notes:

  1. As soon as the user makes a gesture on the document, zooming is enabled again, so if you change the device orientation after that, the zoom bug will still occur.
  2. The user can only effectively start zooming after starting a second gesture.
  1. for the first problem, i am aware of this, additional event handling can be added (on orientation change). but the idea is if someone wants to zoom the text, he may not care about the bug.
  2. this one i can't replicate, if u experience this, can try touchmove?

I can confirm that #1 and #2 occurs for me (iPhone 3GS, iOS 4.3.1).

I can confirm #1 and #2 on iPod touch 4, iOS 4.3.1

@jdalton’s rewrite was so good I ported most of his changes back to this gist for future reference.

Works brilliantly, thank you !!! Very tight nice code too. Like art.

I agree with ibrent. Nice job.

@mbjwork: The license is as liberal as it gets:

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

Tested and working on iPhone 3G with OS 3.1.2 of Safari

Any idea on how to modify this script to make it work when the initial scale has to be 0.5 instead of 1.0? — Please, any help is always welcome.

Hmm, could you not just pull in the min/max from the actual meta tags and only override them if not present?
That might be best for dumb designers like me.

This doesn't seem to fix the bug at all. The point of maximum scale is to lock the width to the width of the device. After zooming with this script, when changing orientation, it still has the problem of being too big.

Also, requiring two gestures seems clunky.

Any test on iOS 4.3.3?

Confirmed working on iPad 4.3.5 (8L1) and iPhone 4G 5.0.1
Confirmed NOT working on iPod 5.0

I think I got a better solution to this bug (just submitted to MBP for evaluation and maybe integration):

https://github.com/sergiolopes/ios-zoom-bug-fix

I face palmed
document.getElementsByTagName('body')[0]

You mean because of document.body? ;-)

This works great but I've noticed it is adversely affecting my href links.

I have my nav links set to width="100%". If I use my finger to scroll and a link is below my finger, it triggers the :hover state of the link (in this case a background color). I'm assuming it has to do with gesturestart. It happens in both the original script as well as in this improved one.

I've heard rumors that this is fixed in iOS6. Can someone confirm this?

@mihaipaun not as far as I can tell...

If that bug was fixed there should be some release information on it somewhere. I'd love to see a link on this to know if it truly is supposed to be fixed. I too have heard the rumors.

I read through what I could find on the iOS 6 release with no luck.

http://mathiasbynens.be/demo/ios-viewport-scaling

In order for the script to work and bypass the 2nd gesture minor tweaking like in orienatation change event set the max to 1.00099 instead of just 1.0

hi, i'm still in a learning process and really grateful to all sites like this one!

the code works fine with me. the only thing is that a tiny part of the page is being cut off from the sides. is there a way of preventing this or is it possibly a self-inflicted problem because i made my page 1000px wide?

i'd be very grateful to any help and ideas!

I appreciate this code, which has helped me as I've adapted my website to be more mobile friendly. I'm posting about an issue which just came to my attention, hoping for some advice. It seems that the bug fix doesn't work if a page includes dynamic text. I have two pages which implement the bug fix, although the script is external in a file named MaintainViewport.js. If you visit http://mauitradewinds.com/test/view.htm you will see a horizontally-scrolling image with a fixed text caption. The viewport bug fix works perfectly. But, at http://mauitradewinds.com/test/test.htm there is a fading caption below the scrolling image. The viewport bug is not fixed on this page, although it references the same javascript to correct that bug. If I remove the dynamic caption, the viewport bug also disappears. If there is a solution to this, I'd be grateful to see it.

}(document));? should be })(document);

@ericmuyser - you can write it either way. The latter is more common, but the former works as well.

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