Some websites are using the following values in the meta viewport <meta name="viewport" content="initial-scale=1.0001, minimum-scale=1.0001, maximum-scale=1.0001, user-scalable=no"> It has unintended consequences in Firefox Android. <meta name="viewport" content="initial-scale=1, minimum-scale=1, maximum-scale=1, user-scalable=no"> The value 1.0001 was used by Web developers to fix an issue with iOS devices when iOS 9 was released. It happened in 2015. Basically, this was a hack to fix a change when rotating the device (in between portrait mode and landscape mode.) WebKit is zooming out the content to fit the full content of the page. But developers needed a "shrint-to-fit=no" (which was added) https://forums.developer.apple.com/thread/13510#60444 Unfortunately many developers have been using the 1.0001 magical values. My hunch is that the magical value comes from https://github.com/WebKit/webkit/blob/04c2bea6721a142bb73f9626e646c5aa5251c2d8/Source/WebKit2/Shared/CoordinatedGraphics/SimpleViewportController.cpp#L118 which computes a boolean for enabling the "scale to fit" with a clamping set at 0.0001 bool currentlyScaledToFit = fuzzyCompare(m_pageScaleFactor, m_minimumScaleToFit, 0.0001);

Note that the site for https://webcompat.com/issues/15180 has dropped the 1.0001 values in some circumstances: They now use including viewport-fit=cover <meta id="viewport" name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1, viewport-fit=cover"> https://webkit.org/blog/7929/designing-websites-for-iphone-x/ Circumstances are determined by the screen size. if (screen.width < 768) { var meta = document.createElement('meta'); meta.name = "viewport"; meta.content = "user-scalable=no, initial-scale=1.0001, minimum-scale=1.0001, maximum-scale=1.0001"; document.getElementsByTagName('head')[0].appendChild(meta); var element1 = document.createElement("link"); element1.setAttribute("rel", "stylesheet"); element1.setAttribute("type", "text/css"); element1.setAttribute("href", "/css/desktop-responsive.min.css"); document.getElementsByTagName("head")[0].appendChild(element1); var element = document.createElement("link"); element.setAttribute("rel", "stylesheet"); element.setAttribute("type", "text/css"); element.setAttribute("href", "/css/mobile-responsive.min.css"); document.getElementsByTagName("head")[0].appendChild(element); } On Chrome the initial size will be 360px and in Firefox it will be 980px. So this will kick back again when we fix Bug 1423709

(In reply to Karl Dubost :karlcow from comment #0) > The value 1.0001 was used by Web developers to fix an issue with iOS devices > when iOS 9 was released. It happened in 2015. Basically, this was a hack to > fix a change when rotating the device (in between portrait mode and > landscape mode.) As per a comment [1] in Apple Developer Forum, the hack was also indented to avoid shrinking wider contents to device screen width even if initial-scale=1 is specified. [1] https://forums.developer.apple.com/thread/13510

It's not yet clear to me why the site in https://webcompat.com/issues/8023 is correctly viewed on normal nightly, but I think we can make this a dup of bug 1494422. Karl?

Hiroyuki, Yes that's interesting it seems it was not working and it's now working. It is currently. ```html <meta name="viewport" content="width=device-width, initial-scale=1.0001, minimum-scale=1.0001"> ``` The maximum-scale value has been dropped and they probably added `width=device-width` Let's make it a dupe indeed. In this one, we get: https://webcompat.com/issues/17551 ```html <meta name="viewport" content="initial-scale=1.0001, minimum-scale=1.0001, maximum-scale=1.0001, user-scalable=no"> ``` I wonder if `width=device-width` is making a difference.