An explanation of layout viewport and visual viewport can be found here.
I have read here and here that one should use
<meta name="viewport" content="width=device-width,initial-scale=1.0">
if one wants to optimize a webpage for mobile devices.
I would like to understand the consequences of this on the iphone4 in landscape mode. I would think that the following happens:
width=device-width
The device width of the iphone4 is 320px in landscape (see here) even though the iphone 4 has a screen-width of 480px in landscape mode. So the layout viewport is set to 320px.
initial-scale=1.0 This sets 1 CSS pixel to 1 device pixel (see here). Now since the iphone4 has a width of 480 device pixel, this implies for me that the visual viewport is 480px wide.
Thus, the layout viewport is set to 320px and the visual viewport to 480px. Doesn't that imply that the webpage is only shown on the first 320 px of the visual viewport and the remaing 160px are left blank?
To give a more concrete example: Consider the following webpage
<!DOCTYPE html >
<html >
<head>
<meta name="viewport" content="width=device-width;initial-scale=1.0" />
</head>
<body>
<div style='background-color:red;width:100%'>Test</div>
</body>
</html>
then in my understanding, this should only fill the screen of the iphone4 in landscape to 320/480=66,66% with red, because the layout viewport would get the length of 320px and since the div-size is relative to the viewport, width:100% is the same as width:320 px, see here:
the CSS layout, especially percentual widths, are calculated relative
to the layout viewport
I am assuming that I am wrong and that the iphone4 will probably display the above page in landscape with 100% red - but why? Have I misunderstood something?
Remark: I found this question Can I have more than 320px content in an iPhone, using viewport tag with device-width and initial-scale = 1? which is closly related to my question but with no answer.
Mozilla's documentation of the viewport meta tag explains this behavior fairly well (https://developer.mozilla.org/en-US/docs/Mozilla/Mobile/Viewport_meta_tag)
For pages that set an initial or maximum scale, this means the width property actually translates into a minimum viewport width. For example, if your layout needs at least 500 pixels of width then you can use the following markup. When the screen is more than 500 pixels wide, the browser will expand the viewport (rather than zoom in) to fit the screen:
<meta name="viewport" content="width=500, initial-scale=1">
By extension, if width=device-width resolves to 320 but the screen is 480 pixels wide, the browser will also expand the layout viewport to 480.
Also from the same document:
Mobile Safari often just zooms the page when changing from portrait to landscape, instead of laying out the page as it would if originally loaded in landscape.
I think that behavior has changed somewhat in recent versions of iOS, but it can be a confounding factor in figuring out what is going on, as on some devices the layout viewport will sometimes be different when a page is loaded in landscape vs. when the page is loaded in portrait and then rotated to landscape.
Mozilla goes on to say:
If web developers want their scale settings to remain consistent when switching orientations on the iPhone, they must add a maximum-scale value to prevent this zooming, which has the sometimes-unwanted side effect of preventing users from zooming in:
<meta name="viewport" content="initial-scale=1, maximum-scale=1">
I'm not a fan of this technique; I think the cure is worse than the disease in most cases.
It is because it is rotating page rendered in portrait mode. You will have to redraw page. Here is similar question .
I think that the problem you have is confusing the device-width and screen/browser resolution.
as in the example you post:
These pixels have nothing to do with the actual pixel density of the device, or even with the rumoured upcoming intermediate layer. They’re essentially an abstract construct created specifically for us web developers.
In other words, width/height mirrors the values of document. documentElement. clientWidth/Height, while device-width/height mirrors the values of screen.width/height. (They actually do so in all browsers, even if the mirrored values are incorrect.)
they are retina display and the difference is only in bigger pixel rendering from the iphone, so the browser will rendere full-screen even with 320px device-width in landscape. the big problem with iphone is that this difference don't change between portrait/landscape.
and
You can set the layout viewport’s width to any dimension you want, including device-width. That last one takes screen.width (in device pixels) as its reference and resizes the layout viewport accordingly.
where the device pixel (The screen) is different from visual viewport
<meta name="viewport" content="width=device-width;initial-scale=1.0" />
there device-width will have always 100% screen width.
<meta name="viewport" content="width=320px;initial-scale=1.0" />
there you should test if there are no changes on iphone or the DIV will extend out/gap of the screen in landscape
i think this source is correct only using media-query with device-width (not visible on iphone), because if you use normal media query you can see that the effective pixel-ratio of the browser rendering changes from 320px to 480px
max-width is the width of the target display area, e.g. the browser; max-device-width is the width of the device's entire rendering area, i.e. the actual device screen.
If you are using the max-device-width, when you change the size of the browser window on your desktop, the CSS style won't change to different media query setting;
If you are using the max-width, when you change the size of the browser on your desktop, the CSS will change to different media query setting and you might be shown with the styling for mobiles, such as touch-friendly menus.
Related
This question already has answers here:
Is the viewport meta tag really necessary?
(9 answers)
Responsive web design is working on desktop but not on mobile device
(4 answers)
Closed 3 years ago.
As far as I was aware, vh and vw used the height and width of the visual viewport - the size of the browser window, and divided it by 100. Therefore, if you defined an element to be 100vw wide, it will always span the entire browser window, what MDN calls the visual viewport.
When working on my website, I found that an element set to 100vw is only taking up a portion of the screen, and that this is only visible on mobile devices - the error is absent until I open the chrome device toolbar.
The dark grey <section> elements are set to height: 100vh; width 100vw;, and I also have
html,body {
height:auto;
width:100vw;
margin:0;
padding:0;
}
I have tried the website on my phone and the error is still present, but it is not present on a resized chrome window. What have I missed?
Live link
Thanks to Temani Afif for pointing me in the right direction. From MDN:
Narrow screen devices (e.g. mobiles) render pages in a virtual window
or viewport, which is usually wider than the screen, and then shrink
the rendered result down so it can all be seen at once. Users can then
pan and zoom to see different areas of the page. For example, if a
mobile screen has a width of 640px, pages might be rendered with a
virtual viewport of 980px, and then it will be shrunk down to fit into
the 640px space.
This is done because many pages are not mobile optimized, and break
(or at least look bad) when rendered at a small viewport width. This
virtual viewport is a way to make non-mobile-optimized sites in
general look better on narrow screen devices.
In order to prevent this, this meta tag is used:
<meta name="viewport" content="width=device-width, initial-scale=1">
This sets the viewport to be fixed to the device width.
When resizing the browser to the width of different mobile and tablet screens, the font seems fine readable and big enough, but when i check the website on my tablet the font seems smaller and not enough readable.
I thought that the browser is a real indicator of what the website should look like in smaller screen devices, but this seems not the case, as font looks small in my tablet screen.
So why font is not shown on the smaller devices as the same as the browser when resized to the same size??
The viewport meta tag tells the browser that your site is responsive ready and allows the browser to scale your site to device pixels rather than actual pixels. This should emulate a narrower viewport with the content appearing larger on screen at a more natural size. This tag should be placed in the head section of your HTML file.
<meta name="viewport" content="width=device-width, initial-scale=1.0">
My site uses bootstrap 3 to accommodate devices of varying screen sizes. I use bootstrap's hidden-xs class to hide my page's unnecessary background image on small devices allowing them to focus on the important input components without having to zoom in. This works fine if you resize the browser window or adjust your monitors resolution. It also works great on low-res phones like the iPhone.
However, since bootstrap uses screen pixel size, this does not work on android phones with high resolutions. The result is, the phone user has to zoom in or work hard to select the appropriate inputs as they appear small on the phone's physically small screen.
Is there an easy fix for this so that users with high-res phones don't get the same look as the desktop users?
Thanks!
You can use this meta tag
<meta name="viewport" content="width=device-width, initial-scale=1">
in the <head> section of your HTML document, to scale the document based on the screen width of the device you are using.
Check MDN for more information about the viewport meta tag and its usage.
I work on a responsive site with media queries for three screen width ranges:
0 - 767 px "mobile" layout
768 - 1023 px "tablet" layout
1024 px and above "desktop" layout
As with every responsive site, each layout's designed to fit nicely and be legible in the given screen size. So the mobile layout works for screens 320 wide, for example.
At the moment we use the meta viewport tag
<meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1">
which stops the user resizing with pinch-to-zoom and makes the different layouts kick in as you resize your browser.
We would like to change this behaviour to restore the user's ability to scale. More importantly, we want to change the behaviour in the middle ("tablet") range, so we have:
0 - 767px - "mobile" layout, as before
768 - 1023px - "desktop" (1024px) layout scaled down to fit in the smaller screen width
1024 px and above - "desktop" layout, as before
This is so our advertisers who sell 970x250 billboards can be assured their ads will be seen by people who view our site on tablet portrait screens.
Can anyone suggest the correct viewport meta tag for this kind of half-responsive requirement? When I remove the current meta tag the whole "desktop" page layout scales down to fit in my iPad screen OK: but then it does the same on my iPhone, so the responsiveness is lost. On the other hand, with
<meta name="viewport" content="width=device-width">
as suggested on CSS Tricks, the responsiveness is fully on again, so the iPad shows the "tablet" layout.
I've tried deleting my 768 media query with all its CSS, but then I just get the "mobile" layout on tablet from the media query for smaller screens.
Is there any straightforward way to do this? Or do I need to change the viewport meta tag with JS, so the page isn't scaled down on mobiles but is at 768? Unfortunately I can't post the URL of our site, but I'm hoping people will understand this explanation.
I have a bit of an issue, I am developing a full HD (1920x1080) website which I also want to be able to use on the iPad retina display (2048x1536) however the iPad is only showing that it has a resolution of (1024x768) despite the specs clearly stating otherwise (http://www.apple.com/uk/ipad/specs/)
If I create a div of width 1024 then it appears full screen on the iPad and a div of 1920 width forces the iPad to scroll?
Does anyone know why I cannot use the full retina display and am forced to 1024x768 resolution on the iPad?
That's an intended behaviour.
Since most web sites still specify their text size in pixels (12px), a retina screen would results in text that is much too small. To avoid this, Safari on the iPad 3rd gen and iPhone 4/4s tell web servers that they have 1/4 the resolution they really have. The text is then rendered in finer details by Safari but it also retains its intended size.
As a workaround, try setting the meta tag "viewport" in your site to allow for a greater resolution.
<meta name="viewport" content="width=device-width" />
Set your initial viewport size to half of it's original size thus creating a canvas that is double the size that the hardware returns (1024px * 2 = 2048px).