About This HTML Issue
The device-width and device-height media features (along with their min- and max- prefixed variants) originally referred to the physical dimensions of the device’s entire screen, regardless of how much space was actually available to the document. In practice, this distinction caused confusion and inconsistent behavior across browsers. On most modern devices and browsers, device-width and width return the same value anyway, making the device-* variants redundant.
The device-* media features were frequently used as a proxy to detect mobile devices, but this was never a reliable approach. A narrow browser window on a desktop monitor would not trigger a max-device-width query even though the available layout space was small. Conversely, modern phones and tablets with high-resolution screens can report large device widths that don’t reflect the actual CSS viewport size. The viewport-based alternatives (width, height, aspect-ratio) more accurately represent the space available for rendering your content.
Using deprecated media features causes W3C validation warnings and may eventually lose browser support entirely. Replacing them ensures your stylesheets are future-proof, standards-compliant, and behave consistently across all devices and window sizes.
How to fix it
Replace any device-width, device-height, or device-aspect-ratio media feature (including min- and max- prefixed versions) with the corresponding viewport-based equivalent:
| Deprecated feature | Replacement |
|---|---|
device-width |
width |
min-device-width |
min-width |
max-device-width |
max-width |
device-height |
height |
min-device-height |
min-height |
max-device-height |
max-height |
device-aspect-ratio |
aspect-ratio |
The width media feature describes the width of the viewport (the targeted display area of the output device), including the size of a rendered scroll bar if any. This is the value you almost always want when writing responsive styles.
Examples
Incorrect: using deprecated max-device-width
This triggers the validation error because max-device-width is deprecated:
<link rel="stylesheet" media="only screen and (max-device-width: 768px)" href="mobile.css">
Correct: using max-width instead
Replace max-device-width with max-width to query the viewport width:
<link rel="stylesheet" media="only screen and (max-width: 768px)" href="mobile.css">
Incorrect: using deprecated min-device-width in a range
<link rel="stylesheet" media="screen and (min-device-width: 768px) and (max-device-width: 1024px)" href="tablet.css">Correct: using viewport-based equivalents
<link rel="stylesheet" media="screen and (min-width: 768px) and (max-width: 1024px)" href="tablet.css">
Incorrect: using deprecated device-aspect-ratio
<link rel="stylesheet" media="screen and (device-aspect-ratio: 16/9)" href="widescreen.css">
Correct: using aspect-ratio
<link rel="stylesheet" media="screen and (aspect-ratio: 16/9)" href="widescreen.css">
Applying the same fix in CSS @media rules
The same deprecation applies to @media rules inside stylesheets. While the W3C validator specifically flags the media attribute on <link> elements, you should update your CSS as well:
/* Deprecated */
@media only screen and (max-device-width: 768px) {
.sidebar { display: none; }
}
/* Correct */
@media only screen and (max-width: 768px) {
.sidebar { display: none; }
}
If your site relies on a <meta name="viewport"> tag (as most responsive sites do), the viewport width already matches the device’s CSS pixel width, so switching from device-width to width will produce identical results in virtually all cases.
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