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In the modern age of web design, understanding media queries is essential if you want the website to be functional on multiple devices platforms. Media queries allow you to conditionally apply CSS selectors based upon the view port, screen size and resolution.

Implementation Theory - Smallest to Largest

The most common implementation theory for responsive website design is the mobile first approach. The concept is you start with the smallest screen and build your core CSS file for those dimensions. Then, for each subsequently larger screen size, you add media queries and additional CSS selectors. Applying selectors from the smallest to largest screen size allow you to minimize the bandwidth requirements for the smartphones by including only small, low-resolution images while allowing for large, high-resolution images to be included on larger screens.

Media Query Syntax

Media queries are implemented using the @media css selector followed by the constraints. The CSS selectors to be applied to the media query are grouped within curly brackets, just like any other CSS selector.

@media (max-width:461px) and screen {

  body { background-color:red; }

}

This would change the background of the body element to red for screen sizes smaller than 461px.

If all of the conditions are true then the media query results to true and the content is applied to the page. Individual constraints can be coupled together with the AND keyword to require multiple constraints to be true. Multiple sets of constraints can be coupled together using a comma separated list (just like multiple CSS selectors) to apply a logical OR situation. Unless otherwise specified, the "all" media type is added to all media query sets, which means an empty set is the same as having no media query wrapper and the selectors are applied in all situations.

Constructing Media Queries

Media query constraints use some of the CSS properties and add a few more to be applicable on the device level. Note, constraints do not always need a value to be applied.

Viewport

The view port is the box in which the page is constructed. This is not always the same as the device width or the browser width. Users can set automatic zoom features which change the ratio between the browser width and the viewport, causing web developers headaches. You can set a scaling ratio for the viewport using the media tag in the html head section.

Constraints

* Dashes (-) indicate the value can be omitted and still work fine.

Legacy and Browser-Specific Constraints

Screen Sizes

If you set the viewport scale to 1, the display dimension is the maximum size of an image you want to include while the viewport dimension is the one you use for your media queries.

In  Practice

It is not practical to create a media query for every single device, specifying its particular dimensions and resolution. Creating a set of breakpoints allow you to format a group of devices, instead of each individual device/screen. Also, setting the viewport scale to 1, simplifies all the artificial display dimensions into a handful of sizes. Adding a min-resolution constraint allows for special styling for those high resolution smart phones.

To assist in the development process, we start with a mobile framework which already has the major break points identified.

Download our framework

Reference

The specifications for media queries can be found at:

• http://www.w3.org/TR/css3-mediaqueries/
• https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Media_queries
• https://developer.mozilla.org/en-US/docs/Mozilla/Mobile/Viewport_meta_tag
• https://www.apple.com/ipad/compare/
• http://support.apple.com/kb/sp622
• https://www.apple.com/iphone/compare/
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