Create responsive AMP pages

Introduction

Responsive web design is about building fluid web pages that respond to your user's needs—pages that fit their device's screen size and orientation. You can achieve this easily in AMP. AMP supports all screen and device categories and provides built-in responsive components.

In this guide, we'll show you how you can easily implement these responsive fundamentals in AMP:

• Controlling the viewport
• Creating a responsive layout
• Scaling media

Controlling the viewport

This section is only valid for AMP websites, ads and stories.

Creating a responsive layout

In responsive design, you can use CSS @media queries to tailor the styling of your web page for various screen dimensions without having to alter the content of the page. In AMP, you can continue to use those same CSS @media queries. Additionally, for finer control over an AMP element, you can specify the media attribute on the element. This is particularly useful when you need to either show or hide an element based on a media query. See the Changing the art direction of an image section for an example that uses the media attribute.

Making each element resize to fit a screen can be tricky. However, in AMP, you can easily make an element responsive by just specifying the "layout=responsive" attribute along with the element's width and height attributes. When you apply the responsive layout to an element, that element will automatically resize to the width of its container element, and the height will change based on the aspect ratio specified by the element's width and height. Almost all AMP elements support a responsive layout; refer to the element's reference documentation to see which layouts are supported.

Even though you can easily make elements responsive with "layout=responsive", you still must consider how your elements appear on all screen sizes--including desktop and tablet. A common mistake is to allow an image to take the full width of the screen, which stretches the image beyond its intended size, causing a poor experience for widescreen users. By default, elements with layout=responsive will take the full width of the element's container, which is often unrestricted in width (ie., width=100%). You can improve how images appear by simply restricting the width of the image's container. For example, by setting a "max-width" rule on the "body" or "main", you can restrict all images to a specific max width.

Example: Restricting width of responsive images

In the following example, we have a flowers image (640 x 427 px) that we want to display on all screen sizes, so we specified the width and height, and set the layout to responsive.

<div class="resp-img">
  <amp-img
    alt="flowers"
    src="/static/inline-examples/images/flowers.jpg"
    layout="responsive"
    width="640"
    height="427"
  ></amp-img>
</div>

However, we want the image to not stretch beyond its intended size, so we set the max-width on the container to 700 px via custom CSS:

<style amp-custom>
  .resp-img {
    max-width: 700px;
  }
</style>

Scaling media for the page

Probably the most challenging aspect of responsive design is displaying media correctly on the page so that it responds to the screen's characteristics. In this section, we'll look at how you can embed responsive media on AMP pages.

Displaying responsive images

Images make up a large part of a web page (approximately 65% of the page's bytes). At minimum, your images should be visible on various screen sizes and orientations (i.e., the user doesn't have to scroll, pinch/zoom to see the entire image). That's easily done in AMP via the "layout=responsive" attribute (see Include Images in AMP). In addition to the basic responsive image, you might want to serve multiple image resources to:

• Serve crisp images for the right resolution
• Change the art direction of an image
• Provide optimized image formats

Serving crisp images for the right resolution

For high-resolution screens (e.g., Retina display), you should provide images that look crisp and sharp; however, you don't want to use that same image on low-res devices because that'll cause unnecessary extra load time. In non-AMP and AMP pages, you can serve the correct image for the screen's pixel density by using srcset with the width descriptor ( w ).

Example: Displaying a crisp image that fits the screen

In the following example we have several image files that are of the same aspect ratio but of different resolutions. By supplying various image resolutions, the browser can choose the image that best suits the device's resolution. Additionally, we've specified the size to render the image at :

• For a viewport width up to 400 px, render the image at 100% of the viewport width.
• For a viewport width up to 900 px, render the image at 75% of the viewport width.
• For everything above 900 px, render the image at 600 px wide.

<amp-img
  alt="apple"
  src="/static/inline-examples/images/apple.jpg"
  height="596"
  width="900"
  srcset="/static/inline-examples/images/apple-900.jpg 900w,
            /static/inline-examples/images/apple-800.jpg 800w,
            /static/inline-examples/images/apple-700.jpg 700w,
            /static/inline-examples/images/apple-600.jpg 600w,
            /static/inline-examples/images/apple-500.jpg 500w,
            /static/inline-examples/images/apple-400.jpg 400w"
  sizes="(max-width: 400px) 100vw,
            (max-width: 900px) 75vw, 600px"
>
</amp-img>

For example, say we have a device that has a viewport width of 412 px and a DPR of 2.6. Based on the code above, the image must be displayed at 75% of the viewport width, so the browser chooses an image close to 803 px (412 _ .75 _ 2.6), which happens to be apple-800.jpg.

Changing the art direction of an image

Art direction refers to adapting an image's visual characteristics for certain breakpoints. For example, instead of just scaling an image as the screen narrows, you might want to serve a cropped version of the image that narrows the focus of the image or you might want to serve completely different images at the different breakpoints. In HTML, you can accomplish this by using the picture element. In AMP, art direction can be achieved by using the media attribute.

Example: Different sized images for different breakpoints

In the following example, we have 3 different cropped images of a cat that we want to display at different breakpoints. So, if the viewport width is:

• 670 px or greater, display cat-large.jpg (650 x 340 px)
• 470 - 669 px, display cat-medium.jpg (450 x 340 px)
• 469 px or less, display cat-small.jpg (226 x 340 px)

<amp-img
  alt="grey cat"
  media="(min-width: 670px)"
  width="650"
  height="340"
  src="/static/inline-examples/images/cat-large.jpg"
></amp-img>
<amp-img
  alt="grey cat"
  media="(min-width: 470px) and (max-width: 669px)"
  width="450"
  height="340"
  src="/static/inline-examples/images/cat-medium.jpg"
></amp-img>
<amp-img
  alt="grey cat"
  media="(max-width: 469px)"
  width="226"
  height="340"
  src="/static/inline-examples/images/cat-small.jpg"
></amp-img>

Providing optimized images

Delivering fast loading pages requires optimized images--in size, quality, and format. Always reduce file sizes to the lowest acceptable quality level. There are various tools that you can use to "crunch" images (e.g., ImageAlph or TinyPNG). In terms of image formats, some image formats provide better compression abilities that others (e.g., WebP and JPEG XR vs JPEG). You'll want to provide the most optimized image for your user, as well as ensuring the image is supported by the user's browser (i.e., not all browsers support all image formats).

In HTML, you can serve different image formats by using the picture tag. In AMP, although the picture tag isn't supported, you can serve different images by using the fallback attribute.

In AMP, there are two way to achieve serving optimized images: server-side and client-side.

Configuring the server to send the most appropriate image format

Developers using image formats that are not widely supported, such as WebP, can configure their server to process browser Accept headers and respond with image bytes and the appropriate Content-Type header. This prevents the browser from downloading image types it does not support. Read more about content negotiation.

Accept: image/webp,image/apng,image/_,_/\*;q=0.8

Using nested image fallbacks

In the following example, if the browser supports WebP, serve mountains.webp, otherwise serve mountains.jpg.

<amp-img
  alt="Mountains"
  width="550"
  height="368"
  layout="responsive"
  src="/static/inline-examples/images/mountains.webp"
>
  <amp-img
    alt="Mountains"
    fallback
    width="550"
    height="368"
    layout="responsive"
    src="/static/inline-examples/images/mountains.jpg"
  ></amp-img>
</amp-img>

As a nice bonus, some caches, like the Google AMP Cache, automatically compress and convert images to WebP and the right resolutions if you don't. However, not all platforms use caches, so you should still optimize images manually on your end.

Examples to inspire you

Here are some examples that we hope inspire you to create responsive AMP pages:

Production

• Getty Images "2016 in Focus"
• BRIT + CO's holiday gift guide
• The Guardian

Made by AMP

• Examples

• Written by @bpaduch
  with contributions from @pbakaus