Cloud Four Blog

Technical notes, War stories and anecdotes

On the Device Context Continuum

The fact the Apple may soon release an App Store for TVs has me revisiting a couple of questions that have troubled me these last few years: Where does the common device context continuum start and end? And more importantly, how do we know?

But before I look at those questions in detail, let’s talk about device context.

The Device Context Continuum

We now design for a continuum of devices. Responsive web design provides us with the techniques we need to design for varying screen sizes.

But responsive web design techniques wouldn’t be effective if there wasn’t a common context—or perhaps more accurately, a lack of context—between devices.

Put a different way, if people did demonstrably different things on mobile phones than they did on desktop computers, then responsive web design wouldn’t be a good solution.

phone-tablet-desktop-continuum

We design for different screen sizes confident in our knowledge that people will do similar things whether they are on phone, tablet or desktop devices. This is our common device context and the continuum that it applies to.

But it hasn’t always been this way.

The Mobile Context Debate

In the early days of responsive web design, people often debated whether or not mobile context was a thing that should be considered in our designs.

At the time, I wrote about my conflicted thoughts on mobile context. I advocated for keeping context in mind. But by 2013, I had concluded mobile context didn’t exist.

Now we have a lot of experience to back up this perspective. Chris Balt, a Senior Web Product Manager at Microsoft, told Karen McGrane and Ethan Marcotte on the Responsive Web Design podcast:

Our data shows us quite plainly and clearly that the behavior of those on our mobile devices and the small screens is really not all that different than the behavior of those on the desktop. And the things they are seeking to do and the tasks they are seeking to accomplish are really quite the same.

Karen and Ethan have been doing a weekly podcast for a year. In that time, regardless of the company or industry being discussed, people say that they see no difference in what people want to do based on whether they are using a mobile, tablet or desktop.

I still think Luke Wroblewski nailed it when he wrote:

But if there’s one thing I’ve learned in observing people on their mobile devices, it’s that they’ll do anything on mobile if they have the need. Write long emails? Check. Manage complex sets of information? Check. And the list goes on. If people want to do it, they’ll do it on mobile -especially when it’s their only or most convenient option.

What about new devices? TVs? Watches?

It seems that not a day goes by without a new device form factor being introduced. Watches. TVs. Virtual reality goggles. Augment reality glasses.

Where do these new devices fit in on this device context continuum? Do they share the same context?

continuum-question

The consensus at the moment seems to be that they are not part of the same continuum as phones, tablets and computers. When you read the guidelines for designing for watches or TVs, designers are advised to take context into consideration.

At Responsive Day Out, Rosie Campbell, who works in Research and Development for the BBC, gave a compelling presentation entitled Designing for displays that don’t yet exist. She shared research on what it would take to build a compelling smart wallpaper experience in the future when such technology might become commonplace.

In the talk, Rosie made two comments that I’ve been thinking about ever since. She addressed what we need to do as screens get weirder:

It’s not just about making content look beautiful on those different screens. We also need to think about what is appropriate for each device because you’re probably not going to want the same kind of information on your smart watch as you want on your smart wallpaper.

This makes intuitive sense to me. For whatever reason, my Apple Watch feels very different than my phone or my computer.

But Rosie also used browsers on Smart TVs to illustrate a point that just because a technology makes something possible, doesn’t mean that we should design experiences around it:

Suddenly, we all got Smart TVs. And it was great. We got Internet on our TVs. But actually browsing the web on the TV was a really clunky experience. It was not very pleasant. And no one really wanted to do it especially when you’ve got a mobile or tablet next to you that makes it easier.

Again, what Rosie states here is the popular consensus that people won’t browse the web on their TVs. Steve Jobs famously said that:

[People] don’t want a computer on their TV. They have computers. They go to their wide-screen TVs for entertainment. Not to have another computer. This is a hard one for people in the computer industry to understand, but it’s really easy for consumers to understand. They get it.

I’ve spent the last three years researching the web on TVs wondering about exactly this question. And it isn’t clear cut to me whether or not people will browse the web on TV screens in the future.

The consensus on mobile context has changed

The popular consensus used to be that no one wanted to browse the web on their phones. If you dared to build something targeting phones, you were advised to keep the mobile context in mind:

  • People are on the go.
  • Devices are slow and clunky.
  • Phones are hard to type on.

Even after the iPhone came out, people argued that yes, the iPhone had a good browser, but that we’ve had browsers on phones for years and no one used them. People simply don’t want to browse the web on their phones.

This seems laughable now, but it was the accepted consensus at the time.

The reason we had a debate about mobile context when responsive design first arrived is because responsive design challenged the widely accepted idea that people wanted to do different things on their phones.

What do we know about how people will use new devices?

Rosie shared solid research on smart wallpaper. The BBC tested their theories and watched people interact with prototypes. Those observations led to their conclusions about where that future technology would go.

But I found myself wondering what researchers in the early 2000s found when they observed people using their phones. Might they have said something like this:

Suddenly, we all got Smart TVs phones. And it was great. We got Internet on our TVs phones. But actually browsing the web on the TV phone was a really clunky experience. It was not very pleasant. And no one really wanted to do it especially when you’ve got a mobile or tablet next to you computer that makes it easier.

I’m not picking on Rosie here. I do this myself. My gut instinct is to agree with her in many ways.

I find myself thinking, “Well clearly watches are a different thing.” I have similar thoughts about screens in odd places like refrigerators. They don’t feel like they part of the same device context continuum.

But how do I know? I used to think that phones were a different thing.

Predicting future behavior is difficult

Because I was on the wrong side of the mobile context debate, I’ve become leery of our ability to predict future behavior.

In 1994, the New York Times published an article asking “Has the Internet been overhyped?” People were looking at usage of AOL and Prodigy and trying to understand what the impact of the web was going to be.

On a smaller scale, we’re often told that a web site doesn’t need to worry about mobile because the analytics show that people don’t use that site on mobile.

To which I counter, “Why would anyone use your site on mobile if it isn’t designed to work well on those devices? How do you know what people will do after it has been designed to work well on small screens?”

I now have a fundamental rule: we cannot predict future behavior from a current experience that sucks.

Where does the device context continuum end?

All of which brings me to back to my original questions: Where does the common device context continuum start and end? And more importantly, how do we know?

continuum-happy

I’m uncomfortable with the current consensus. Particularly when it comes to TVs. It feels like Justice Potter Stewart saying “I know it when I see it.” It makes me wonder if we’re in the feature phone era of TVs.

I want some guidelines to help me know when something is going to be part of the device context continuum and when it won’t. Some questions we can ask ourselves about devices that will help us see if our current views on a particular device’s context are real or simply artifacts of a current, flawed implementation.

And I wonder if what I wish for is simply impossible in the present.

Thanks to Tyler Sticka for the illustrations.

The feature phone era of TVs ends next week

Three years ago after writing Head First Mobile Web with Lyza, I was burnt out on mobile and wanted to do something different. So I decided to start researching the web on TVs.

TVs seemed like the furthest thing from mobile devices. Before his death, Steve Jobs had told his biographer, Walter Isaacson, that he had “finally cracked” TVs. Rumors were flying that Apple was getting into TVs in a big way.

Photo of TV

So I set off to find out what it might be like to design and build for the web on TVs. I’ve given a few talks on TVs and it has shaped the way I look at the web.

But I’ve never found the time to write about it. With Apple rumored to release its new Apple TV next week, it seemed like the right time to share what I’ve learned.

When I’m looking at TVs and what is possible on them, it doesn’t matter much to me whether the features are being provided by a set top box, game console or the TV itself. I realize that is different when someone makes a purchasing decision.

I’ve focused on Smart TVs because Anna Debenham has done extensive testing on game consoles already and there is less known about Smart TVs. But most of what I’ve found still rings true when I’ve tested game consoles and set top boxes.

No one knows what they’re getting when they buy a Smart TV

The first thing I learned about TVs is how incredibly difficult it is to find TVs that you can test on. Best Buy has walls of TVs, but only three of them had accessible remote controls and were on the Internet.

I fared a little better at Fry’s where the TVs had remote controls, but no Internet. So I tethered the TVs to my phone and watched them start downloading long-overdue software updates:

One of the many TVs that updated firmware using my phone's connection

Eventually, I found a local store, Video Only, that had TVs on WiFi. They’ve been great. I’ve returned every year bearing a box of donuts and a series of tests to conduct.

I drove to several stores before I found one that made it easy to test the smart features of these TVs. Average consumers won’t do this. They have no idea how what their Smart TV can do nor how well it does it before they buy it.

Smart TVs are computers, but no one sells them that way

The discovery happened by accident.

I was at Best Buy using the only TV that was on the Internet that had a remote. I was digging around in some of the Smart TV settings when I happened to notice a tiny progress bar in the lower right corner:

Surprising storage usage indicator

Wait… what? This TV has a storage limit?

Of course it makes sense that the TV would have a storage capacity. The reason why this surprised me is because I had not seen a single sales tag or spec sheet list the storage capacity of the TV.

Even today TV manufacturers will brag about their app stores, they will tout their fancy Octo-core processors, but they don’t list the basic storage capacity.

Good luck even finding the name of the operating system they are using let alone what the current version is.

These TVs are computers. They have downloadable apps. They have various CPU speeds. They have storage limits.

And yet, not a single store nor manufacturer sells them as if they were computing devices. I’m not saying TVs should be sold like a Windows machine, but there is no difference between how TVs are sold now than how they were sold in the 80s.

There is no Smart TV market

Because I spent hours testing TVs in the stores, I was able to observe dozens of people shopping for TVs. In all that time, I never heard a single person ask specifically for a Smart TV.

They asked if the TV supported Netflix.

Remote control with Netflix button

Sometimes they would ask about Hulu or Amazon Video. But they’d never dive deep into the Smart TV features. Even at Video Only where the TVs were on WiFi, only a small percentage of people would ever check out the Smart TV menus.

So while it is difficult to find TVs that don’t have some Smart TV capabilities, I don’t believe you can have a Smart TV market when no one knows what they’re buying and no one is asking for Smart TV features.

Web rendering on TVs is surprisingly capable

I’m going to go into more detail about what I found when testing browsers on TVs another day, but the short version is that the rendering engines on Smart TVs are generally equivalent to same era iPhones.

Both the 2015 LG and Samsung TVs have higher scores on HTML5Test than my iPhone 6 running iOS 8.4.1 does.

2015 LG TV scores 495 on HTML5Test.com

That’s not to say that the web browsing experience is necessarily good. It can be clunky especially if the remote only features a d-pad. But in general, the problem isn’t the rendering engine.

Input remains the biggest challenge

The moment you move away from changing channels and start interacting with the Smart TV functionality, input becomes the biggest challenge. Remote controls are cumbersome and crude input devices.

Over the years I’ve seen TV manufacturers try all sorts of ways to make remote controls better including:

Sony Google TV remote featuring keyboard on back, touch pad on front, and every button you could ever want.

  • Full keyboards
  • Miniature keyboards
  • Motion detection
  • Gesture
  • Touchpads
  • Voice control
  • Smartphone apps

To their credit, TV manufacturers keep looking for ways to make input work better. But no one has cracked it yet.

The Feature Phone Era of TVs

The more I studied TVs, the more I was struck by the similarity between the TV market of today and the phone market before the iPhone was released.

Timeline of phones showing how they changed after iPhone release

Before the iPhone came out, nearly every phone manufacturer had their own operating system. It was often hard to know what the operating system was called and what version you were using.

Input was difficult, slow and frustrating. People advised those who built for phone to keep in mind the mobile context.

Companies touted the ability to install apps and browse the web, but the experience was terrible so few used those features.

The phone manufacturers believed they had a mature market and that they understood what people wanted from their phones. They laughed at the optimism for the iPhone saying that browsers have been on phones for years and no one used them.

There are echoes of each of these in the current TV landscape. And again Apple stands poised to enter the market in a big way led by what sounds like an innovative form of input.

Will Apple pull it off? I don’t know.

But I can tell you one thing, I’m ready for the feature phone era of TVs to end.


Will someone do this on mobile?

A frequent question that product owners face is whether not someone will do a particular activity on a mobile device or not.

In my experience, people often arrive at two answers based on context.

  1. When looking at your own product:
    Of course, no one would ever try to do this on a mobile device.
  2. When using someone else’s product:
    Of course, this should work on mobile.

Design accordingly.

Responsive Images, Part 10: Conclusion

Phew. We made it! We’ve come to the end of the Responsive Images 101 series.

Before we part ways with this series, I want to pass along some tips, resources and final thoughts on where responsive images are heading next.

Responsive image audits

Were this a book, I would have devoted a chapter to responsive image audits. It is the first thing we do when we start looking at how to convert a site to responsive images.

And it is most likely your next step towards taking what you’ve learned and applying it to your sites.

Fortunately, I wrote about these audits in great detail recently. Instead of repeating it in the 101 series, I encourage you to read what I wrote about responsive image audits now. Consider that article Part 9a.

Compatibility

Browser support for responsive images standards is growing rapidly. As of August 2015, Chrome, Opera and Firefox all support picture, srcset, sizes, and type.

Microsoft Edge and Safari support srcset with display density (x) descriptors, but not the width descriptors. Microsoft has started development to support the full responsive images standard.

Apple hasn’t committed to supporting the standard yet, but Apple knows responsive images support is important and Yoav Weiss has been contributing to the WebKit implementation.

When it comes to image-set(), there is still a lot more work to be done.

PictureFill

But even if all the browsers currently supported the responsive images standards, we’d still need a way to help older browsers understand the new syntax. That’s where the PictureFill polyfill comes in.

PictureFill will allow you to use the new responsive images syntax now.

Automating your image processing

In Part 9, I said that humans shouldn’t be picking image breakpoints. Instead, we should have software doing this automatically for us.

I want to expand on this point and say that most of what we deal with when it comes to responsive images is not something that designers and developers should be thinking about on a regular basis.

The goal for most organizations should be to centralize image resizing and processing and automate as much of their responsive images as possible.

In my ideal world, a responsive images workflow for resolution switching would look something like this:

  • Where possible, use resolution independent SVG images.
  • When creating or modifying the design of templates, the template author provides the sizes attribute for the various images in the template.
  • The srcset attribute with width descriptors is inserted by the server which does all of the heavy lifting of figuring out what image breakpoints to choose for each image.
  • Content authors never worry about any of this. Their only responsibility is to upload the highest quality source available and let the image resizing service take care of the rest.

This isn’t a far-fetched scenario. Many organizations already have image resizing services. And if your organization doesn’t, I maintain a spreadsheet of image resizing services and tools that you can consider (be sure to read the explanatory blog post as well).

And many content management systems are starting to look for ways to incorporate responsive images. The Responsive Images Community Group (RICG) maintains a WordPress plugin and they are currently looking at how to add it to WordPress core. Drupal 8 will ship with a responsive images module (more details).

The only thing these image resizing services need to add is support for figuring out how many image sources to supply for a given image and to output the proper markup for those image sources. They may not even need to worry about the markup if Client Hints takes off.

(More on Client Hints soon. This is a 201 topic.)

But regardless of how you automate it, I believe that centralizing image resizing and processing is essential to maintaining your sanity. When we talk to new companies exploring responsive images, one of the first things we assess is their image workflow and how much of it we can automate.

Future of responsive images

We’re just getting started when it comes to responsive images. We have thousands of sites to update to use the new image standards. Many organizations need to update how they handle images to centralize and automate what has until now been a manual process.

Even though there’s still a lot of work ahead of us, it feels like we’re finally on the downhill slope. We’re no longer struggling to find solutions that everyone can agree on. Implementations are landing in browsers. We have PictureFill to help us fill the gaps.

And now the wider web development community is beginning to look at how they are going to implement these new standards which means that we can start learning from each other.

If you’ve read this entire 101 series, you have everything you need to get started with responsive images. I can’t wait to see what you do with the new standards. Please share what you learn!

Thank you for reading.


Responsive Images 101 Series
  1. Definitions
  2. Img Required
  3. Srcset Display Density
  4. Srcset Width Descriptors
  5. Sizes
  6. Picture Element
  7. Type
  8. CSS Responsive Images
  9. Image breakpoints
  10. Conclusion

Responsive Images 101, Part 9: Image Breakpoints

I’ve dreaded writing this installment of the Responsive Images 101 series. Selecting image breakpoints is something everyone will face, and frankly, I have no good answers for you.

But sooner or later, we will all face the image breakpoints koan. We might as well start now.

What are responsive image breakpoints?

In our responsive layouts, breakpoints refer to the viewport sizes at which we make changes to the layout or functionality of a page. These typically map to media queries.

Responsive image breakpoints are similar, but slightly different. When I think about image breakpoints, I’m trying to answer two questions:

  • How many image sources do I need to provide to cover the continuum of sizes that this image will be used for?
  • Where and when should the various image sources be used?

The answers to these questions lead to different breakpoints than the criteria we use to select breakpoints for our responsive layouts. For our layouts, we follow Stephen Hay’s advanced methodology: We resize the browser until the page looks bad and then BOOOOM, we need a breakpoint.

With the exception of art direction, the main reason why we need multiple image sources has nothing to do with where the images look bad. We want to provide multiple image sources because of performance concerns, different screen densities, etc.

So we can’t simply reuse our responsive layout breakpoints for our images. Or I guess we can, but if we do so, we’re not really addressing the fundamental reasons why we wanted responsive images in the first place.

Image breakpoints for art direction is relatively easy

In situations where the image falls under the art direction use case, the art direction itself will often tell us how many image sources we need and when they should be used.

If you think back to the Nokia browser site example, we can tell when the image switches from landscape to portrait mode. When that switch occurs, we know we’re going to need a new source image.

However, this may only be part of the picture. What if one of the art directed images covers a large range of sizes. We may find that we still need to have multiple sources that don’t map to the art direction switch.

You can see an example of this in the Shopify homepage that we looked at in Part 8.

Shopify home page animated

Despite the fact that the image only has one major art direction change—from the full image to the cropped one—Shopify still provided six image sources to account for file size and display density.

<picture>
  <source srcset="homepage-person@desktop.png, homepage-person@desktop-2x.png 2x"       
          media="(min-width: 990px)">
  <source srcset="homepage-person@tablet.png, homepage-person@tablet-2x.png 2x" 
          media="(min-width: 750px)">
  <img srcset="homepage-person@mobile.png, homepage-person@mobile-2x.png 2x" 
       alt="Shopify Merchant, Corrine Anestopoulos">
</picture>

So knowing that an image falls under the art direction use case can give us some clues, but it doesn’t answer all of our questions about the necessary image breakpoints.

What about resolution switching breakpoints

This is where things really get tricky. At least art direction provides us with some hints about how many image sources might be needed.

So long as we’re downscaling flexible images, they will always look good. We can’t rely on them looking bad to tell us when we need to change image sources.

Let’s take a look at a resolution switching example:

Photo of Michelle Obama at three sizes

In this example, we have a photo of Michelle Obama where the image in the page is 400 x 602 pixels for the current viewport size. The largest size that the image is ever displayed at is 2000 x 3010 pixels. That large file is 250K.

We can simply shrink that 2000-pixel image, and it will look good. But it would be unnecessarily large. It would be better if we provided a smaller version like the one 800 x 1204 resolution image that is shown in the example. That image is only 73K.

We can all agree that when the image in the page is only 400 x 602 pixels in size, that providing an image that is 800×1204 and 73K is better than having people download the largest version of the image.

But why stop at 800×1204?

Michelle Obama example with a fourth size at 600px wide

If we provided another image source that was 600×903 pixels wide, it would only be 42K. That saves us 31K (42%) from the 800×1204 image.

Well shoot. A savings of 42% is a big deal. Maybe we should keep going. 500 pixels wide? 450 pixels wide?

Photo of Michelle Obama with examples at 450 and 500 pixels wide

Each smaller image source offers the potential for substantial savings over the previous size. If we keep on this track, we eventually end up with an image source that is the exact size of the image in the page.

So here’s the question that has vexed me about image breakpoints. How do I know when an image source is too big for the size that the image is being used in the page?

The answer is that unless the image source matches exactly the size that the image is being displayed in the page, it is always going to be too big. There is always going to be an opportunity to optimize it further by providing a smaller image.

Why not provide the exact size of the image?

At this point, you may be wondering why we simply don’t provide the exact size of that the image is going to be used in the page.

First, the whole point of flexible images in responsive design is to provide images that scale as the size of the viewport changes. If we provided images that were exactly the size used in the page, we’d likely need to download new images whenever the viewport size changes or the device was rotated.

Second, it is unrealistic to provide images at any size imaginable. Yes, we can dynamically resize images, but when we resize images, the server needs to do that work which slows down delivery of that image to the browser.

For this reason, most larger sites cache images on content delivery networks (CDN). Caching every image size possible on the CDN would be incredibly expensive.

Finally, the browser doesn’t know the exact size of the image in the page when it starts downloading. That’s what got us to new responsive images standards in the first place!

Possible ways to pick image breakpoints

As I mentioned at the beginning, I have no rock solid solutions for how to pick the number of image sources that you need. Instead, I want to describe some different ways of looking at the problem that may help inform your decisions.

Winging it (aka, matching your layout breakpoints)

Someone on your team says, “Hey, how many source images do you think we need for these product photos?”

You ponder for a moment and say, “Hmm… how about three? Small, medium and large.”

Don’t be ashamed if you’ve done this. I’m pretty sure almost every person working on responsive images has done this at some point.

Perhaps your organization still thinks about mobile, tablet and desktop which makes small, medium and large make sense.

Or maybe you take a look at the range that the image will be displayed and make your best guess. Perhaps you simply look at the number of major layout breakpoints and decide to do the same for your image breakpoints.

I completely understand. And this is better than providing one huge image for all viewports.

But it sure would be nice to have more logic behind our decisions.

Testing representative images

If guessing doesn’t seem like a sound strategy, then let’s insert a little science into the art of picking image breakpoints. We can take a look at some representative images and figure out how many breakpoints they need.

The hardest part of doing this is determining representative images, or figuring out if you have any at all.

For some sites, all the photographs may have a particular style dictated by the brand. If that is the case, finding representative images is easy. Pick a few images and then resize them and save them at sizes ranging between the largest and the smallest images until you feel like you’ve got decent coverage.

Of course, if your site has a diversity of image styles, finding representative images can be nearly impossible.

Memory usage influencing the distribution of image breakpoints

Earlier this summer, Tim Kadlec gave a presentation on Mobile Image Processing. In that presentation, he took a look at the memory usage of flexible images in responsive designs.

What Tim showed is that as an image gets bigger, the impact of resizing an image gets larger.

Memory usage of two different images

In the example above, reducing a 600×600 pixel image by 50 pixels in each direction results in 230,000 wasted bytes versus the 70,000 wasted bytes caused by reducing a 200×200 image by 50 pixels in the exact same way.

Knowing this tells us a bit about how we should pick our breakpoints. Instead of spacing out breakpoints evenly, we should have more breakpoints as the image gets larger.

graph showing more breakpoints at large sizes

Unfortunately, while this tells us that we should have more breakpoints at larger sizes, it doesn’t tell us where those breakpoints should be.

Setting image breakpoints based on a performance budget

What if we applied the idea of a performance budget to responsive images? What would that look like?

We’d start by defining a budget for the amount of wasted bytes that the browser would be allowed to download above what is needed to fit the size of the image in the page.

So say that we decided that we had a performance budget of 20K for each responsive image. That would mean that we would need to make sure that the various sources that we’ve defined for the image are never more than 20K apart.

When we do this, we find that the number of image breakpoints change wildly based on the visual diversity of the image and the compression being used.

Let’s take a look at three sample images.

Time Square — 8 Image Breakpoints

Times Square

This image has a lot of visual diversity. The variations in colors and textures means that JPEG’s lossy compression cannot do as much without damaging the image quality.

Because of this, there are eight image breakpoints—set at 20k intervals—between the smallest size of the image (320×213) and the largest size of the image (990×660).

Breakpoint # Width Height File Size
1 320 213 25K
2 453 302 44K
3 579 386 65K
4 687 458 85K
5 786 524 104K
6 885 590 124K
7 975 650 142K
8 990 660 151K

Morning in Kettering — 3 Image Breakpoints

Morning in Kettering

Unlike the Times Square image, this image has a lot of areas with very similar colors and little variation. Because of this, JPEG can compress the image better.

On an image that can be compressed better, our 20K budget goes farther. For this image, we only need three image breakpoints to cover the full range of sizes that the image will be used at.

Breakpoint # Width Height File Size
1 320 213 9.0K
2 731 487 29K
3 990 660 40K

Microsoft Logo — 1 Image Breakpoint

Microsoft Logo

This is a simple PNG8 file. At its largest size (990×660), it is only 13K. Because of this, it fits into our 20K budget without any modifications.

Breakpoint # Width Height File Size
1 990 660 13K

Take a look at the other images on a sample page we created. See how the number of breakpoints vary even through all the images start with the same resolution end points.

Now, I’m not suggesting that you manually decide on image breakpoints for every single image. But I can envision a future where you might be able to declare to your server that you have a performance budget of 20K for responsive images and then have the server calculate the number of image sources on a per image basis.

I’ve written in more detail about performance budgets for responsive images in the past. If you end up implementing this approach, please let me know.

Setting image breakpoints based on most frequent requests

At a recent Responsive Images Community Group (RICG) meeting, Yoav Weiss and Ilya Grigorik discussed a different way of picking image breakpoints based on the most frequently requested image sizes.

For both Yoav, who works at Akamai, and Ilya, who works at Google, one of the problems they see with multiple image sources is storing all of those sources on edge servers where storage is usually more limited and costs are higher.

Not only do companies like Akamai and Google want to reduce the number of images stored at the edge, but the whole purpose of their content delivery networks is to reduce the amount of time it takes for people to render a web page.

Therefore, if they can cache the most commonly requested image sizes at the edge, they will deliver the fastest experience for the majority of their users.

For these organizations, they can tie their image processing and breakpoints logic to their analytics and change the size of the images over time if they find that new image sizes are getting requested more frequently.

When combined with the new HTTP Client Hints feature that Ilya has championed, servers could get incredibly smart about how to store images in their CDNs and do so in a way that requires little to no decision-making by designers and developers.

Humans shouldn’t be doing this

I believe that in a few years time, no one will be talking about how to pick responsive image breakpoints because no one will be doing it manually.

Sure, we may still make decisions for images that fall into the art direction use case, but even then, we’re probably not going to make finite decisions about every image source. We’ll handle the places that require our intervention and let our image processing services handle the rest.

There is a ton of benefit to either picking image sources based on a performance budget or based on the frequency with which different sizes of the image are requested. But either of these solutions are untenable as part of a manual workflow.

In the future, our typical workflow will be that we upload the highest quality image source into our content management system or image processing system and never have to think about it again.

Part 10 of a 9-part series

This started as a 9-part series, but there is always more to discuss when it comes to responsive images. Read for the conclusion of this series where I’ll provide some essential resources and talk about what the future holds for responsive images.


Responsive Images 101 Series
  1. Definitions
  2. Img Required
  3. Srcset Display Density
  4. Srcset Width Descriptors
  5. Sizes
  6. Picture Element
  7. Type
  8. CSS Responsive Images
  9. Image breakpoints
  10. Conclusion